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Oral History Transcript — Dr. Gerald Kron

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Interview with Dr. Gerald Kron
By David DeVorkin
In Flagstaff, Arizona
May 20, 1978

open tab View abstract

Gerald Kron; May 20, 1978

ABSTRACT: General interview examining family origins; early life in Milwaukee; interest in mechanical things; development of interest in astronomy; engineering at University of Wisconsin, Milwaukee campus; interest in photoelectric photometry; graduate study at Madison and work with C. Huffer and I. Stebbins; Stebbins and A.E. Whitfordís work; graduate study at Lick Observatory and Berkeley; photoelectric instrumentation; Lick in the pre-war years; World War II at MIT and Caltech; return to Lick and use of lP2l photomultipliers; W. Baade; origin of 120-inch telescope; Australia; Lick during the 1950s and C.D. Shaneís retirement; the electronic camera; contacts and association with H. Johnson, M. Walker and Lallemand; move to Flagstaff and the Naval Observatory; recollections of Lick staff in 1930s; H.N. Russell; Mrs. Kronís work at Harvard and astronomical interests.

Transcript

DeVorkin:

I know you were born in Milwaukee in 1913.

Kron:

Yes. Thatís right.

DeVorkin:

Iíd like to know more about your family origin, and some of your early interests.

Kron:

Well my father was a descendant of a German immigrant who came to this country about 1840 and the family reached back to a town called Czernowitz whose possession is sometimes by Poland, sometimes by Russia and sometimes by Czechoslovakia. The family moved west, bit by bit. First they moved to Germany where one of the members was involved with the University of Heidelberg and then finally they moved to the United States and to Milwaukee. My mother is (sheís still alive at 95) a Connecticut Yankee type whose family had lived in North Dakota for a while; and then part of the family moved to Milwaukee where my parents met. I spent all of my life in Milwaukee until I went to California in 1935 for the first time. I went to Milwaukee high schools which in those days were very good, and then to the University of Wisconsin where I spent five years getting a Degree in mechanical engineering and another two years in astronomy under Stebbins.

DeVorkin:

Okay letís deal with your life in Milwaukee, your home life, what the influences were upon you. What were your parentsí interests.

Kron:

Well my mother had no interests outside of the home but my father was very mechanically oriented and when he was a very young man, before I arrived on the scene, he did machine work. He was a machinist and later on in order to survive during a time when I guess there wasnít much need for machinists he became a private chauffeur. He was driving for a very wealthy family in Milwaukee about two years after I was born. I lived in the same house from the age of two until I left home in 1935 at age 22. So I lived in that house for twenty years in Milwaukee.

DeVorkin:

His mechanical interests, when do you think you first became aware of them and how did he involve you with this?

Kron:

Well he had a lathe at home that he purchased after heíd realized he could probably continue to be a private chauffeur and in order to indulge his enthusiasm for machine work. When I was about six or seven years old he bought castings for and made a steam engine, of course, which flamed my imagination. And when I became old enough, that is when I was in high school (at the age of about 12), I learned how to run the lathe and I began to make my own engines and other things. I made projects in high school for the year end exhibitions that they had. Whenever I worked on projects, even if it was for English, for example, it usually had machine shop overtones.

DeVorkin:

Youíve shown me some of your early models. What models in particular did you work on, what were your interests?

Kron:

Well my interests were in the overall concept of creating a mechanical device, mainly in those days; a steam engine. They are simple to understand and are fun. And so with my fatherís help I saw through the construction of several steam engines, taking the design from a model making book that my father had for many years. I made the castings from wooden patterns. We made our own molds, poured our own metals and then machined the parts in the lathe to a finished engine. I made several of them. In fact I sold one to the Physics Department of our local high school as a demonstration steam engine. So my own personal interests lay along highly mechanical lines and I kept on even after I went to college in Madison. I got an entry to the studentís machine shop in physics department in Madison and this kept me in touch with physicists, although I was taking mechanical engineering course at the time. So I took extra classes in physics and mathematics while I was there to augment my engineering studies.

DeVorkin:

This was at Madison?

Kron:

This was at Madison.

DeVorkin:

What about your high school science experience?

Kron:

I took all the shop and science courses in high school and unfortunately avoided languages but fortunately I took all of the English courses too, and all of the mathematics.

DeVorkin:

Are there any teachers that you recall being significant on your development?

Kron:

Yes. There were some very good teachers. I had an extremely good shop teacher who kept an interest in me later on, in fact I got a letter from him within the last ten years, heís a very old man. He may not still be alive. And I had a very good teacher in physics who took a personal interest and who was working at Madison to get a Masterís Degree in physics in order to improve his prestige in the Milwaukee public school system. And then I had an excellent English teacher. I can still remember her name, and a fairly good mathematics teacher in trigonometry and in algebra.

DeVorkin:

Do you remember the names of any of these teachers?

Kron:

The algebra teacher was Miss Tainsch, the English teacher was Miss Reynolds, the shop teacher was Mr. Dunlop. And the physics teacher was Mr. Suchy. He was central European, very dark man. Milwaukee had representatives of all kinds of Europeans. What would be called now minorities. Lots of Polish, people who we called Italians and who were really Sicilians. They were all in ghettos in the sense that they lived together. There was a Hungarian region, a Polish region in town, and we lived in the Sicilian one. So that I got to know a lot of these people quite well, the people who were regarded as national minorities. And of course there was this undercurrent of German immigrants that formed the nucleus of the development of the city of Milwaukee. The Scandinavian influence with which the State of Wisconsin is ordinarily associated isnít felt in Milwaukee. Itís spread through all the rest of the State but Milwaukee was mostly German and Polish and Sicilian.

DeVorkin:

Thatís an interesting blend. During any of this period did you have contact with astronomy? Did you have an interest at all?

Kron:

Yes. My father was very much interested in astronomy. As a private chauffeur we used to accompany the very wealthy family we worked for to a lake in the lake region of Wisconsin every summer. This was Oconomowoc Lake. An historian has written that this is a famous lake because it was practically owned by many wealthy Milwaukee people. And an historian recently finished a book on the subject of the town of Oconomowoc and the lake and its background culture and as a chauffeurís son I have been mentioned very favorably in this book as having had an influence, in the local culture.

DeVorkin:

You had an influence or you were influenced by?

Kron:

No I had an influence in the local, culture because of the things I did all the time; I was always active.

DeVorkin:

What did you do?

Kron:

I had a friend there who belonged to a Scottish family, the Lindsay family, a very large family. He and I bought parts for old motor bikes out there and with $5.00 worth of parts we managed to assemble an operating motor bike and would dash around the countryside on unpaved roads without a license using old cleaning fluid for fuel. Our money for the summer was gone, you see. The $5.00 had to be used for the motor bike, so we couldnít buy gas and certainly not a license which would have cost another $5.00.

DeVorkin:

This was in the Ď20ís?

Kron:

This was in the mid Ď20ís. We built boats and I built two power boats that operated with my steam engines and sailed them on the lake and this attracted crowds of people.

DeVorkin:

Were these models?

Kron:

Oh yes, model power boats.

DeVorkin:

Nothing large enough to sit in.

Kron:

No. Thatís what I wanted. I had an ďawfulĒ desire to have a boat that I could actually ride in, and this was heightened by the fact that the Pabst[1] youngsters, who were about my age at the time, actually had a boat like that. They managed to get a gasoline engine. I had to hand it to them, papa did not buy them an expensive boat, they made it. But they could afford the wood. They made the whole boat, they bought the engine and they installed it with a stern tube. It was propeller driven. I had several rides in it. Thatís what I wanted too, except I wanted it to be powered by steam but I couldnít even afford to buy the wood to make the boat. Nowadays if I were on a body of water again Iíd probably do this. I still have the enthusiasm now for that I should think. It has to be something secluded and with a sympathetic atmosphere.

DeVorkin:

Why?

Kron:

Well this brings us face to face with the present American culture I think, in which everything has to be brand new, chrome plated and very powerful. The motor boats that you see on the lakes all have about 500 horsepower V8 engines that stick up out of the top with chrome plated exhaust pipes and fiberglass hulls that look as if they could do 100-miles an hour. This is not my idea of fun. But my idea of fun is practiced on the Upper Thames, upstream from London. Thereís a little factory called the Stuart-Turner Company that turns out parts for boats like this. They turn out the engines finished and unfinished and the hardware, boilers and the propellers and the stern tube equipment.

DeVorkin:

This is full size?

Kron:

This is the sort of thing that would drive a little fifteen foot launch.

DeVorkin:

Thatís the same company you mentioned that manufactured models.

Kron:

Yes. The ones for driving such a launch are much bigger than the models that I showed you, quite a bit larger. But the engine that would drive a boat like that would weigh only about 75 pounds. The local people there build the boats and buy their hardware from Stuart-Turner and go chugging around on the Thames. Now see there you are among people who have the same idea of fun that I do.

DeVorkin:

Thatís interesting. About your interest in astronomy, how did it develop, you were talking about the lake?

Kron:

Well, you see, there were dark skies up there and my father took an interest from an astronomical point of view in things in the sky, not astrological at all. There used to be a series of child-oriented editorials in the Milwaukee Newspaper, it was called Uncle Rayís Corner. And Uncle Ray would discuss educational and creative things in the world of biology, physics and chemistry and astronomy. To help me, my father used to cut out the ones that were astronomical and made a scrapbook for me and I studied these and got an interest in astronomy through those. But when I got to college age my parents prevailed. I wanted to take either chemistry or astronomy. But my parents thought that there wouldnít be a good enough income in that, so they prevailed on me to take mechanical engineering, for which of course I was quite well suited. So I did, and got a Masterís Degree in mechanical engineering, five years in mechanical engineering. And then I changed to astronomy after I finished.

DeVorkin:

Was there any question where youíd go to college or when did it become apparent that you would go to college?

Kron:

Well I donít think we ever felt any other way. It was just a natural extension of oneís education. The first two years at that time could be undertaken in Milwaukee which meant that I had no housing expense or anything like that. I used to walk to school and I know this sounds a little like the chappy who walked through three feet of snow, you know, five miles to go to grammar school, but it wasnít quite that bad. I did walk about four miles to school and walked back home, generally. Partly for the exercise. I got out of physical education by doing that for one thing.

DeVorkin:

Why was that?

Kron:

I didnít like physical education, I didnít like basketball and things like that. I still donít. I think sports are silly and a waste of time. If you need exercise you get it in a whole lot of other things that are adapted to your own needs or conveniences. At the present time I do a lot of walking too, just for exercise, but I wouldnít want to play basketball.

DeVorkin:

Did you build a telescope?

Kron:

Yes.

DeVorkin:

Were you still in Milwaukee at that time?

Kron:

Yes. As a matter of fact I started the telescope when I still lived in Milwaukee all the time, when I was going to what they called the university extension division in Milwaukee. And I finished it after Iíd gone to Madison. The thing that gave me the impetus to finish is that I had a pattern making course in Madison as a part of my mechanical engineering training, and they had quite a large foundry there. Needless to say the instructors were simply tickled pink to have a student who took an interest in this and wanted to make something instead of just regarding it as part of his training and wanting to get it over with as soon as possible. So I built the telescope the way I built my little engines, by making the patterns in the pattern shop as part of my pattern making training, making the castings in the foundry as foundry training and then I did as much machining as I could. Some of the parts were too big to machine in the student machine shop there. So I had a little machining done in Milwaukee, which during the depression cost practically nothing. I finished the telescope and set it up in Madison and used it.

DeVorkin:

Whereís the telescope now?

Kron:

Itís up in the attic here in the house.

DeVorkin:

What size is it?

Kron:

6-inch.

DeVorkin:

I think that would be a very interesting item to preserve.

Kron:

Yes, we intend to preserve it, itís hard not to, it would break your heart to discard anything like that and I doubt if anyoneís willing to buy it, so I think weíll save it. Itís nominally my sonís property now.

DeVorkin:

Which one?

Kron:

Richard.

DeVorkin:

Heís the one thatís going on pretty much in astronomy?

Kron:

Yes.

DeVorkin:

Would it be something we could see just briefly a little later?

Kron:

Oh yes.

DeVorkin:

Great, weíll get to that. Did you have any friends who had similar interests as you were growing up in Milwaukee?

Kron:

Yes, I had two very close friends about the same age. One of them went to the high school that I attended and became, I think through me, interested in machine work. The two of us instead of spending our time after school at high school age doing nothing, would always rush to our house and start up the lathe and turn out a little engine part. And then another one I met when the two of us, myself and this same boy, went to the Milwaukee extension division, was David Parkinson who was part of the Kerst-Parkinson team who developed the pressure van de Graaf at Madison. Letís see, Parkinson, Kerst, there was another one, Kerst developed the betatron. Herb, Parkinson and Kerst were the three. Ray Herb was the oldest of the bunch and was an instructor at the time in the physics department at Madison, Parkinson was my pal who learned how to do machine work through me, how to run a lathe, and Don Kerst was the brains of the Herb-Parkinson-Kerst outfit. Parkinson designed and built a lot of the equipment for the first pressure van de Graaf. Herb masterminded it, in the sense that he took care of the relationship between this development and the physics department, the financing and all of that. And then Kerst was the one who managed the ionization chamber design and the general electrical design of the interior, of the van de Graaf generator and things like that.

There was an interesting story connected with that. It was supposed to be a vacuum van de Graaf, and of course they could not — with all the crud in the tank like rubber belts and everything — even begin to get a high enough vacuum. So they decided to make it a pressure van de Graaf which worked very nicely. And then someone found that some of the organic related vapors would improve the breakdown characteristics, so they put carbon tetrachloride in the tank and greatly enjoyed about twice as much voltage as they ever had before and sat around listening to it break down inside. It sounded as if someone in the tank were hammering on it with a sledge hammer; I was there at the time listening to this. Then they shut it down and about a week later they tried it again but it didnít work at all. When they took it apart they found that the electrical discharges had decomposed the carbon tetrochloride into carbon which contaminated everything and chlorine which destroyed everything that wasnít contaminated. (laughter)

DeVorkin:

Thatís too bad.

Kron:

This was just a small unit, the big one that was taken down to Los Alamos later on was a later development. The one that was destroyed was just a model, you see, to see if it would work.

DeVorkin:

When did you build that spark generator?[2]

Kron:

I built that when I was a senior in high school, that was my exhibition project in physics in 1929, when I graduated from high school. I got out of high school in June in 1929 and then the depression came the month before I went to college. I would have gone to Madison right away except for that — the difficulties caused by the depression. I spent two years in Milwaukee extension. Didnít do any harm I think.

DeVorkin:

In building the spark generator did you build it from plans?

Kron:

I copied one that was the property of the physics department in high school. I simply made a Chinese copy of it.

DeVorkin:

What about the basic electricity underlying it?

Kron:

Oh that was simple. There was no problem about that, itís just an induction generator.

DeVorkin:

At that time you had enough physics to understand it?

Kron:

Oh yes certainly. There was a lot of emphasis on static electricity in those days. When you studied physics you always got a good understanding of static, the electronics of static electricity I guess youíd call it.

DeVorkin:

Okay, letís move on to Madison, the first two years in Milwaukee as you said, any significant teachers at that time in preparing you?

Kron:

Yes. I had a significant teacher in physics. He was Miles J. Martin and he had a Ph.D. from Madison. He has no middle name, just J. He was a very lively person and he hired me as a laboratory assistant in the physics department, and when he found out what I could do at home I began to earn a little more by making instrumentation for the physics department both there in Milwaukee and at Madison. And so when I came to Madison I was known in the physics department and someone said: ďwhy youíre just a kid, I thought youíd be an old German, after seeing the things I built at home.Ē Thatís where I met Parkinson, he was also a laboratory assistant. They needed two because Martin needed lecture assistants and since we were both students we couldnít be there for all the lectures. As a result of what the two of us could do Dr. Martin bought a lathe, a brand new lathe, this was the first new lathe Iíd ever run in my life. And thatís how Dave Parkinson learned how to operate a lathe. We built quite a bit of major equipment, we made a dandy Tesla Coil and large AC magnets for various demonstrations. The department had just been started and had almost no equipment. So Parkinson and I together furnished a great deal of the first instructional equipment used in that department in Milwaukee. We made it ourselves.

DeVorkin:

Did you make any optical equipment?

Kron:

No, no optical equipment. We made electronic equipment. We made a 2.5 meter oscillator, for example, after seeing one out at Madison that had been bought. Parkinson and I made one when we got back. Martin used to take us out to Madison once in a while, particularly to get liquid air. Martin used to give what he called liquid air lectures, you know, this can be quite spectacular. So the two of us used to help when heíd give public lectures in Milwaukee. Parkinson and I used to help and whenever he went to get the liquid air heíd drive to Madison and take us along, so we would meet people in Madison and especially in the Physics Department.

DeVorkin:

Had you met any astronomers before you got there?

Kron:

No I didnít. I missed meeting Stebbins then. When I was in my early days in high school I wanted to have a light sensitive device and Stebbins was doing photoelectric photometry and a description of this got into an old hard cover book that someone gave me. There were some things in that book about the selenium cell. And one time when my parents drove out to Madison when I was still in elementary high school I went to the observatory there to see if I could find someone who knew about photo-cells. Stebbins was still there but I didnít get a hold of him; instead I got the professor on the staff and he gave me some verbal information about selenium cells but I didnít get a selenium cell. I was hoping that there would be enough feeling of fellowship.

DeVorkin:

Who was the person you talked to?

Kron:

C.M. Huffer.

DeVorkin:

How did you get interested in light sensitive surfaces?

Kron:

I developed a desire to have a power boat that was operated remotely. And since radio was restricted by licensing conditions and so on, I thought one way to operate a power boat remotely would be with a light beam, you see. You could code light flashes and operate a stepping relay. But I was never able to do it because I couldnít get the right kind of a light sensitive unit. At the time a photo-emissive cell would have cost two or three dollars and was beyond my financial ability, and also beyond my technology because the current was so small. But I could have used a selenium cell and I was never able to get one. There was a place in Milwaukee that sold delightful things like telephone and telegraph relays and sounders and keys and things like that and small electric motors and I always hoped theyíd have a selenium cell but they never did. I didnít even see a selenium cell until many, many years after the time I wanted one so badly. And then when I saw one it was one I made myself.

DeVorkin:

So you went to Milwaukee in Ď29 and Ď30, you got to Wisconsin in Ď31?

Kron:

Yes. I started classes in Madison in 1931.

DeVorkin:

And during this time youíve had no contact with astronomers?

Kron:

No contact with astronomers at all, in 1931 or Ď32 or Ď33 because Ď31 I was in Milwaukee, Ď32 and Ď33 I did undergraduate work in Madison and had no contact with the astronomers except I went to the observatory on one visitorís night. Then in Ď34 I started doing my graduate work in mechanical engineering but then I started to cultivate the friendship with the astronomers, this was Huffer. Stebbins was a formidable man there and he was hard to see. Huffer was the person who guarded Stebbins and he was the one you saw if you went into the observatory. You usually didnít get beyond him to see Stebbins. But I learned a little about what the observatory was doing and saw the telescope and talked to Huffer about photoelectric work and got an interest in it. When I got my Masterís Degree in mechanical engineering I had two chances to get a job, one was at Grinnell College in Iowa teaching, and the other one was at a factory in Milwaukee that was called a Washer factory, and when I got there to have a look at the conditions I didnít stay to find out whether they made equipment to wash clothing or whether they made little round discs with holes in the middle.

DeVorkin:

It was pretty bad?

Kron:

It was terrible. It looked like a 17th century England sweat shop and so I didnít care for it. My parents agreed that the best thing would be to go back to school and I got a scholarship. I was interviewed by Stebbins, and he conditionally took me on.

DeVorkin:

Why conditionally?

Kron:

Well I think he wanted to be certain that Iíd have a permanent interest. He didnít want to have anything to do with someone who wanted to spent time in astronomy waiting for the Depression to weaken and then go back into some other profession. He wanted someone who would stay.

DeVorkin:

Did he think of astronomy as a haven during the Depression?

Kron:

No, but someone else might have you know, and I think he wanted to guard against getting anyone who felt that way and who would dash off for another job as soon as he found one.

DeVorkin:

He really didnít have any graduate students at that time?

Kron:

I was the only one.

DeVorkin:

Whitford was around at that time?

Kron:

Whitford was never a graduate student in astronomy. He was Stebbinsí assistant from the physics department. Stebbins always got his assistant from physics. And at the time I was a graduate student there was another man there who was Stebbinsí assistant from the physics department.

DeVorkin:

Who was he?

Kron:

Edwin Burnett. He later went to the Naval Research Laboratory in Washington.

DeVorkin:

When was your first exposure to the electrometers that they were using at that time, the string electrometers?

Kron:

They hadnít used the string electrometer for years, but at the time that I came there in 1934 they were still using the Lindemann electrometer. But it was definitely phased out by the time Whitford had a practical operating amplifier outfit, a thermionic amplifier. At the time I came there they didnít actually have it on the telescope. I can still remember the Lindemann electrometer device on the telescope. But by the time I began to do my own observing they had the thermionic amplifier operating and never went back to the electrometer.

DeVorkin:

How was it to be the only student, did you take classes or tutorials, or what?

Kron:

I took classes along with other regular classes. The main one that I had was a class in navigation which taught you spherical coordinates and it was a very good course for a practical beginning in astronomy because you learned all the things that most people donít like to learn. All the ďpick and shovelĒ work all at once in one class.

DeVorkin:

Did Huffer teach that?

Kron:

No, Stebbins taught that himself. Later I took a course from Huffer, a Russell-Dugan-Stewart[3] course. And then with this I took mathematics and more physics and I did a piece of original work in solving the problem of a eclipsing binary. The system Boss 5070.

DeVorkin:

Thatís right. That was published in AP. J. 82 (1935) p. 235.

Kron:

1935; thatís right. Huffer ordinarily did that but this one had some problems that Huffer couldnít solve right off. I stuck with it and got orbital elements for it. There was a sequel to it. It turned out that the observations werenít very good and so it looked as though it had two partial eclipses and that was the cause of the problem. It was a total and annular eclipse and that wasnít obvious from the light curve. The work I did on it didnít show it but I managed to get elements anyway and Stebbins was very pleased by that and that I had learned to write reports. This I got from a course called ďSteam and GasĒ in mechanical engineering in which you were marked one third on accuracy of your result, one third on your comprehension of the experiment (this was with heavy machinery; big steam engines and refrigerators and internal combustion engines), and one third on your English. So it was one of the best courses I had in engineering because I learned to write well enough to write an acceptable paper in astronomy.

DeVorkin:

So that was the training really for your astronomical papers?

Kron:

Yes, thatís right.

DeVorkin:

Huffer had shown you this problem directly? Is this how you became aware of Boss 5070?

Kron:

I think that Stebbins and Huffer talked about it and decided that this would be a good thing to give me. I worked with a manually operated calculator. I think it was a Monroe mechanical calculator.

DeVorkin:

What was the relationship between Huffer and Stebbins?

Kron:

Huffer and Stebbins? Well I would say it wasnít very intimate. Stebbins was an extraordinary person. He established a very formal formidable facade with the result that very few people ever saw him physically. He hung out in the library of the Washburn Observatory there. His desk was there. The Washburn Observatory had a dome for the 15-inch telescope, and connected with the dome at the west end of the building, was a meridian circle building. They had one of the great old Rhepsold meridian circles. And then there was a narrow waist that had the clocks and Huffer in it that connected with the library where Stebbins held forth, you see. And the entrance to the building that was supposed to be used was the entrance to the library but Stebbins had that locked all the time. The entrance that was actually used was the entrance that lead to the 15-inch dome. So to get to Stebbins you went into the hallway that lead to the 15-inch dome. Then you turned right going to the east and went through this relatively narrow part of the building where the clocks were and Huffer held out, and then down a still narrower hall that had the radio equipment for time signals and an entrance to the nether regions where the shop was; and then you gave off into the library and there was Stebbins. You came to him last. And Huffer seldom went in to see Stebbins, and Stebbins never came out to see Huffer that I know of. And so while I was there the first year, in 1935, I dealt mostly with Huffer. And then I was very suddenly accepted by Stebbins as a personal student. From then on I went to California and assisted at Mt. Wilson and then Stebbins got me my entry to the University of California. I did quite a bit of shop work there too. Stebbins bought a new lathe and I set up a machine shop and from then on the machine work at the Washburn Observatory was done by me instead of by the machinists in the physics department.

DeVorkin:

Was it to save money?

Kron:

I think it saved him money because there were transfers of funds from one department to another. And for the price of a lathe why Stebbins no longer had the expense of having machine work done. I made several gadgets for improving the photometer and also some optical equipment. I made optical equipment there and quite a bit of electronic equipment.

DeVorkin:

Had the photometers gotten involved enough for Fabry lenses and that sort of thing?

Kron:

No. The photometers that were used at the time I came there had no Fabry lens but they didnít need it and they still donít on those conditions. They were strictly stellar photometers and the pin-hole optics of the stellar photometer are good enough. You donít need a Fabry lens.

DeVorkin:

No matter what the scale is or anything?

Kron:

Thatís right. But as soon as you widen the field and want to do anything much larger than a star that say an aperture of more than 30 or 40 seconds of arc then you should have a Fabry lens. The one that we used for six-color photometry of globular clusters had a Fabry lens. That was the first photometer made there that had a Fabry lens. It was used only at Mt. Wilson.

DeVorkin:

That was while Stebbins was a Research Associate there?

Kron:

Thatís right.

DeVorkin:

He took Whitford out there usually?

Kron:

Whitford lived there for awhile. Whitford lived there in 1934 and 1935. Stebbins and I drove out to California in June 1935 and Whitford and Stebbins and I all worked up at Mt. Wilson where Whitford and I served as observing assistants.

DeVorkin:

That was your first contact with Mt. Wilson?

Kron:

That was my first contact, yes. And I was light enough physically so that in running the photometer at the three mirror cassegrain focus of the 60-inch, I could ride on the telescope. It was way up in the air you see, we were doing globular clusters that were way south and I could get up and sit on the telescope and run the photometer on the telescope.

DeVorkin:

Who did you meet there? Did you meet Hubble?

Kron:

Oh yes, I met Joy, I met Hubble, and Harold Babcock. Of course Horace Babcock and I were contemporaries and got our Ph.D.ís at Berkeley at the same time. And I met Roscoe Sanford, he was really a very nice guy. And Milton Humason. I got to know all of them quite well as a matter of fact because we went back the next year. So I spent two summers at Mt. Wilson as an observing assistant with Stebbins.

DeVorkin:

During the year you were there, if I recall correctly, Theodore Dunham was back at Princeton.

Kron:

Yeah, although I met Dunham, he was in Pasadena at least once while I was there. I know him very well now.

DeVorkin:

You are both involved in the FAR?[4]

Kron:

Yes.

DeVorkin:

Weíll talk about that a little later. During all this time, Whitford was working with Stebbins, what was Hufferís role in the whole business because he started pretty much as Stebbinsí assistant?

Kron:

Yes he did. Huffer represented the visible instruction part of the astronomy department at the University of Wisconsin. He held all the classes except the navigation class. Stebbins devoted himself mainly to research and administration and taught navigation.

DeVorkin:

Thatís interesting. Why did he single out navigation do you think?

Kron:

I donít know.

DeVorkin:

I talked to Huffer. He had some very interesting recollections about the development of the instrumentation itself. Now during your years there at Wisconsin the instrumentation was developing and you certainly did go into that aspect yourself, was it while you were still there that you and Whitford designed an automatic guider?

Kron:

Yes it was. What happened was that Whitford, Stebbins and I drove back to Madison in 1935. Whitfordís tenure at Cal Tech came to an end, and that was the problem we addressed ourselves to. The 200 inch telescope was very visible at that time in the design state and it had a lot of money. Stebbins got a grant from the 200-inch fund for developing an automatic guider. Whitford and I were the ones that were selected to do the automatic guider development for the 200-inch telescope.

DeVorkin:

What ever happened to it? Did it work?

Kron:

Yes, it worked, not on the 200 inch. It worked in 1937 on the 60-inch at Mt. Wilson. It was only a one dimensional guider, it wasnít intended to be functional. It was intended to investigate the principal of the roof reflector.

DeVorkin:

You had the beam going out in two different directions?

Kron:

Yes. And then two mirrors that ran the beam down to the same light sensitive gadget. I made all the optical parts.

DeVorkin:

Going back a bit to the time when you went and applied to Stebbins for graduate work, did you definitely make the overture to Stebbins?

Kron:

Oh yes.

DeVorkin:

It was not the other way around?

Kron:

No. I went and asked him if I could, and he said: ďyou want to get a Ph.D.?Ē and I hadnít thought about that. And I looked at Stebbins and I thought: ďIíd better get a Ph.D.Ē and so I said I did.

DeVorkin:

What was he like? You said he was aloof.

Kron:

Yes. He was a very charming person who didnít want many people to know him. I made one trip to California and back with him. Thatís correct, I made only one trip to California, because the second time we went to California we went with Whitford and I didnít come back, I stayed, you see. So I made one trip to California and back, the trip coming back was with Whitford too, and we had just a wonderful time just talking and discussing the features of the country. Iíd never been west of the state line of Wisconsin in my life before. And so both Whitford and Stebbins enjoyed seeing the effect on someone like myself, seeing mountains for the first time and being at high elevations and all these things and just the things that went on, the places we stopped to eat and the cabins that we stayed at. They were called cabins then and some were modern cabins with toilet facilities. But most of them werenít modern they were just cabins.

DeVorkin:

Did you talk astronomy?

Kron:

Yes, quite a lot. We also talked railroads. Stebbins was an old railroad man — his family was a railroad family. And so whenever a railroad train would come along weíd have to stop and watch it when we were driving, so Stebbins could watch the train and see it and have full effect on him.

DeVorkin:

Did it make the trip a bit longer than it should have?

Kron:

No, it made it more interesting I think.

DeVorkin:

You took the Northern route?

Kron:

Yes, and came down through Salt Lake City and towns like Nephi. Itís a Mormon town, south of Salt Lake City. We spent the night there and the next day we went to Zion Canyon and Bryce.

DeVorkin:

Do you recall any of the conversations or Stebbinsí interests in the ultimate problems of astronomy? I know the type of work he did with Huffer and with Whitford on B-stars became quite important work.

Kron:

They got the first direct evidence or the first real measurements on reddening, interstellar reddening.

DeVorkin:

Trumplerís work was out about that time.

Kron:

Of course Trumplerís work started this. Trumplerís work started an enormous flap in astronomy in that day, because everyone realized that if Trumpler was right, and he had evidence that left no doubt that he was right, all the distances were off and the peculiar distribution of the globular clusters were suddenly explained and the analogy between the ďham and the sandwichĒ of external galaxies was explained.

DeVorkin:

The ham and the sandwich?

Kron:

Yes. The reddening, the absorbing layer. They look like sandwiches with a black thing, two sides of bread with a black thing between them. They used to refer to it as the ham and the sandwich.

DeVorkin:

Who?

Kron:

Stebbins did that. He had a good sense of humor.

DeVorkin:

When they started finding this, were you involved in that?

Kron:

Not directly, no, just as an assistant, an observing assistant.

DeVorkin:

When they started finding that did they realize that this would change the scale of the galaxy?

Kron:

Yes. Thatís why they wanted to make measurements. And all that B-star work and the work on the globular clusters were all directed toward making measurements that would result in quantitative evaluation of this, you see. What they did was to reduce the globular cluster distribution from a cigar shaped mass to a spherical one.

DeVorkin:

How were your interests developing while you were working for Stebbins as a student? You were going for an M.S. in engineering. Do I have that right?

Kron:

Yes.

DeVorkin:

You didnít get any academic degree in astronomy from the University of Wisconsin? But how were your interests developing?

Kron:

Well at the time I was in Wisconsin they really didnít develop into any creative work in astronomy. I was still doing machine work and it was there that I learned electronics though, from Eddie Burnett. Burnett did most of the electronics work when Whitford wasnít there. The year that I was there and Burnett was there, Whitford was in Pasadena. So Stebbins needed other people to take care of the technological aspects of his work of which he had almost no grasp at all. When the electrometer went out of service, why Stebbins was in the dark about equipment.

DeVorkin:

He understood the electrometer?

Kron:

Yes, but not thermionics.

DeVorkin:

Now thermionics began with Whitford?

Kron:

Whitfordís amplifier, yes.

DeVorkin:

Thatís an external amplifier, do I have that right?

Kron:

Well, you mean physically or electrically?

DeVorkin:

One required a high current at the electrodes.

Kron:

Oh, yes this was an external amplifier. You started with a diode photocell and then the output of the diode photocell went into something they used to call an electrometer tube. And the output of that could be coupled to a galvanometer. So the electrometer tube was really an impedence transformer, so the almost infinite impedence of the photo cell could ultimately operate a low impedence device like a galvanometer. And once that was working, Stebbins was almost in a tizzy for fear it would stop working when Whitford wasnít there. So he hired Eddie Burnett to oversee that and I began to take a deep interest in electronics as a result to exposure to Burnettís enthusiasm and great skill in electronics. He was very good.

DeVorkin:

So thatís the origin of your interests?

Kron:

Thatís the origin of my interests in the practical development of the facility with vacuum tube electronics.

DeVorkin:

Okay weíve been talking about the early work on B-stars and the contacts at Mt. Wilson. We were basically talking about the growth of your interest in astronomy while you were working for Stebbins and I donít think weíve gotten through that. In your position, being hired to do the technical work for a man who, as youíve now indicated, was allowing the technical parts of his research to get away from him to a certain extent. Is that a fair statement to say?

Kron:

Yes, I think so.

DeVorkin:

What did you see your own future as in astronomy?

Kron:

Even by the time I went to Lick I really wasnít interested in astronomy as a career because partly I didnít think Iíd get a job and I think it was partly because up to that time I was more interested in the technical part of astronomy, in the instrumentation part, than in astronomy itself. I developed an interest in astronomy itself at the Lick Observatory when I became interested in my first problem, my thesis problem.

DeVorkin:

But your thesis problem included both the design of a photometer and an eclipsing binary.

Kron:

Thatís right, but by the time the photometer was finished my own attitude had changed, up to that point the photometer was the end in view. When I started work on the star, though, my career in instrumentation became incidental. My real interest turned to astronomy. When I worked on the electronic camera, I did it partly because I had an astronomical project in mind but I was never able to exploit it at Lick, of course.

DeVorkin:

Even though this is out of context what was the specific astronomical problem that you had in mind for the image tube?

Kron:

Well, Shane and Mayall and I had plans, at the time we were top dogs at the Lick Observatory, for an elaborate program of detailed photometric observations of galaxies. We were going to observe galaxies in certain regions of the sky from the point of view of explaining the large amount of absorption that the galaxy counts then indicated. And we were going to do this by cooperating on a great photometric project using the 120-inch telescope for very faint galaxies and we were going to divide the spoils. I was going to study reddening and Mayall was going to study morphological characteristics of galaxies, and Shane was going to use the data to try and explain the absorption indicated by the galaxy counts. I wanted to use the electronic camera for some of that work, for the difficult parts of that work.

DeVorkin:

Well weíll talk about that as we go.

Kron:

It never came to pass so thereís nothing to talk about really.

DeVorkin:

Okay. I want to know why it didnít come to pass. Well the Lick Observatory Bulletin that had your thesis in it was number 499, Volume 19, and the title was the ďNew Photoelectric Photometer at the Lick Observatory.Ē It was published actually in two papers?

Kron:

I think it was. Oh yes, the results of my thesis work were published in two papers.

DeVorkin:

The part of it that was astronomical was your study of the variable YZ Cassiopeia?

Kron:

Thatís right.

DeVorkin:

Thereís two lines we want to go with this. First the development of your interest in astronomy while at Lick. Who you talked to, who was most inspiring to you and the general atmosphere of Lick when you arrived as a Lick Fellow. And the other half of course would be the construction of the equipment itself and your contact with Mr. James Cosh, a person you mentioned who was the man who actually built it. Which would you like to take first, the instrument or the astronomical problem?

Kron:

Letís start out with the instrument. When I came to Lick and I guess weíre there now, is that right?

DeVorkin:

Yes.

Kron:

Well I was surprised to find some of Stebbins' influence there. Stebbins had overseen the construction of a string electrometer type of photoelectric outfit for the 12-inch telescope. That equipment was all still there, the string electrometer. But above all the photo cell was there and when I came to Lick and was asked by W.H. Wright, the director, to build a photoelectric photometer for the 36-inch refractor I had only a foggy idea of how this could really be completed because at the time I came I didnít even have a photo cell and at that time I didnít know there was one at Lick. And had I known I wouldnít have thought it would have been useful. So I kept corresponding with Whitford and Stebbins. Whitford on the details of construction and Stebbins on the acquisition of photo cells from his old friend Jacob Kunz.

DeVorkin:

Kunz was still around at that time?

Kron:

He was still around and I actually bought two cells from him for the enormous sum of $25.00 each.

DeVorkin:

$25.00 each? The price has gone up a bit.

Kron:

Yes. Meanwhile the photometer was being built in the shop by Mr. James Cosh and I started poking around in the instrument storage room at the Lick Observatory and found the quartz Kunz cell still in its original holder that was used on the 12-inch with the string electrometer. That had been there since 1926 or 27, somewhere in there.

DeVorkin:

And who was interested at Lick in such things?

Kron:

A woman. Elizabeth Cummings. She was an assistant at the Lick Observatory at the time. And she published a paper with it. I think Elizabeth Cummings had something to do with the photometry of asteroids using the 12-inch telescope and that outfit. Thereís a LICK BULLETIN on that.

DeVorkin:

I believe it was Max Aitken who had the recollection of helping someone with a very early device such as that, but he couldnít remember who it was.

Kron:

It was probably Elizabeth Cummings.

DeVorkin:

The Aitkens were certainly there at that time.

Kron:

And Stebbins had been there, of course that was the Lick connection. The Lick-Madison axis was partly Stebbins.

DeVorkin:

From the turn of the century. So that did exist there, very interesting.

Kron:

Yes. And I found the quartz photo cell and I knew that in all other respects except the possibility of the Cathode still being good, it would be a good cell. I corresponded with Stebbins about it and he said it was a magnificent cell but he wasnít sure it was still good because Kunz cells didnít always last. And I know now why that is. But at the time apparently nobody knew. The Kunz cells were formed by having a massive substrate of potassium and the surface was formed into the sensitive surface; what happened with time is that the chemical action of the formation of the surface into the hydride would penetrate into the massive potassium underneath and so the chemistry of the surface changed with time. The result was that a Kunz cell was never as good shortly after it was made, by shortly after I mean within a few weeks, as it was when it was made. But some of them kept deteriorating to the point where they were no longer useful at all; others leveled off and stayed good for years. And it turned out when I started to use it, that the Kunz cell at Lick was excellent. It was one of the best cells probably in the country at the time. And this plus the big telescope which for the time was large for photoelectric work you know, and the use of the Whitford amplifier formed a powerful system.

DeVorkin:

You did use it on the 36?

Kron:

Oh yes, extensively. I used the multiplier on the 12-inch later on.

DeVorkin:

Okay weíll get to that.

Kron:

We will.

DeVorkin:

So you used the Kunz cell but I would like, to know the following: you said that Wright had asked you to build this photometer.

Kron:

Yes. They wanted to go back into photoelectric work. They saw the way through to the end of the bright star spectroscopy program with the Mills Spectrograph. Trumpler saw his way to the end of the two prism spectroscopy of cluster stars. And nobody could see what to do next with the 36-inch except to go back to large scale double star measuring, you see. Of course there would always be a background of spectroscopy that never ends but the big programs were coming to an end — the things that could be predicted. So they wanted more predictable work to do with the telescope and they settled on doing variable star work photoelectrically, partly as a result of the Stebbins, or the Madison-California axis. Also partly because of the availability of me, and partly because both W. H. Wright and J. H. Moore had had interests in electrical work with the telescope.

DeVorkin:

I wasnít aware that they had electrical interests other than they were working for Campbell and then Aitken after that.

Kron:

Yes, but they both had interests in photoelectric work and I think it was probably stimulated when Stebbins was there in 1926 or 27, about that time.

DeVorkin:

They chose double star work, binaries. Was that partly influenced by Aitken?

Kron:

Oh you mean for eclipsing variables?

DeVorkin:

Yes.

Kron:

No, I chose that. You see the alternative, for the use of the 36-inch, would have been to go back to visual double star work.

DeVorkin:

Which was truly Aitkenís line.

Kron:

That was Aitkenís line, but he was gone by then. Although Moore and Wright were at the time even regarded as old fogies, they did want to direct the work of the 36-inch into something that was modern for the times — something new. So they picked the photoelectric work. And I can see now, although I have no definite evidence about it, that probably the fact that I went there was planned by Stebbins and Moore and Wright — probably almost at the time I went to Stebbins to ask. They may have been working on Stebbins at the time to get someone from Stebbinsí department to do this. Thatís a guess, I donít know if that true or not. Everything went so smoothly for me that it often seemed as if the way had been greased ahead of time, somehow.

DeVorkin:

So you found things very easy?

Kron:

Oh yes, everything that I needed I got, everything went the way I wanted it to go, and it all seemed to cater to me personally. And it could be that all these plans were made by these old boys ahead of time, you see, to be used by anyone who came along who showed promise. And I just wandered in at the right time.

DeVorkin:

One would hope that we could retrieve that supposition on your part, which makes sense, through the Lick archives sometime.

Kron:

It could be, if some of the letters that went back and forth could be found.

DeVorkin:

At least the direction is now on the tape, maybe someone will do that in the future. Did you take any courses at Berkeley?

Kron:

Oh yes. Yes I took courses under Leuschner a good deal, and Shane.

DeVorkin:

Shane was still at Berkeley?

Kron:

He was completely in Berkeley giving courses in astrophysics.

DeVorkin:

And this would constitute your primary astronomical training?

Kron:

Yes. That plus the constant exposure to astronomers at the Lick Observatory. I spent about half my time on Mt. Hamilton and half my time at Berkeley during two years.

DeVorkin:

How was the relationship between Berkeley and Lick at that time?

Kron:

It was perfectly alright. There was a good understanding among the people of the two departments. But I got into a little trouble because of a strong tendency to identify myself with the Lick Observatory which of course was entirely unjustified. I was a student. But the privileges I had at the Lick Observatory were equal to the privileges of any staff member there. And so I drifted into a state of mind in which I identified myself as a research astronomer instead of a student. And so I was reprimanded a little bit very gently several times for this.

DeVorkin:

By whom?

Kron:

I think Leuschner mentioned it one time. He felt that I should have more loyalty toward the Berkeley department. I should remember that after all I was just a student and things like that. He was quite right. Iím not sure it was Leuschner, it may have been someone else. It wasnít Shane.

DeVorkin:

Leuschner of course taught, his forte was celestial mechanics, comet orbits.

Kron:

Yes. He was totally immersed in that and practical astronomy, the use of transit instruments.

DeVorkin:

So where did your double-star interest come from when it came time to choose a problem, was it from Huffer?

Kron:

It was from Huffer. Of course the only work in astronomy Iíd ever done was on Boss 5070 you see. It developed an interest in the possibility of getting limb darkening coefficients for another star from my courses in Berkeley.

DeVorkin:

And this is from Shaneís influence?

Kron:

This was from Shaneís influence, yes. And so it looked like a fine chance to combine three things, an interest that Shane had stimulated, my previous experience with orbits of eclipsing binaries, and the use of the photometer on the 36-inch telescope. It was beautiful. I had one other idea. And this you will find, I think, interesting. At the time that I was trying to decide definitely on a thesis project, and in those days it was humiliating if you couldnít think of one yourself.

DeVorkin:

Really?

Kron:

Oh yes.

DeVorkin:

So it wasnít expected that your advisor would shove one at you?

Kron:

Not at all. Students like Horace Babcock and Dan Popper and I referred to Trumplerís thesis when we wanted to denegrate a colleague or something.

DeVorkin:

What does that mean?

Kron:

Well, Trumpler had so much ďpick and shovelĒ work to be done that when a student couldnít think of his own thesis problem he was assigned to Trumpler who would carve out a little thesis problem out of his great study of open clusters. Trumpler had so many of these, such a great potential for these little thesis problems that whenever a student seemed unable to think of his own problem why he was handed to Trumpler who would then assign something to the student and have a thesis.

DeVorkin:

But this is no way reflected on Trumpler?

Kron:

Oh no, not at all. Anyway, the three of us who were contemporaries there, always looked down on people who had to resort to Trumpler for a thesis. Well what I was saying was when I wanted to make a final decision about a thesis problem, one of the things I thought of was to try and detect polarization in starlight by means of photoelectric methods.

DeVorkin:

No kidding?

Kron:

Yes.

DeVorkin:

In the late Ď30ís?

Kron:

I had to decide on a thesis subject in 1937. And I talked to Wright and Moore about this and they said: ďItís a fortunate thing you talked to us about this because we already know all about this — in such and such a year this was done photographically by someone, I canít remember who it was, who proved definitely that there was no polarization in starlight.Ē

DeVorkin:

This is what they said to you?

Kron:

Yes. So I gave it up.

DeVorkin:

That explains why it was such a surprise when they found it in the late Ď40ís.

Kron:

Yes, thatís right. That was kind of funny but I think that in what I did, I had a much greater possibility of having a positive result. Suppose I had gone into it anyway. As I saw it at the time the chances were that I would find there wasnít any. And my thesis would consist of telling people that there wasnít any polarization and I wanted to be able to tell people what there was. So I preferred the other subject. I think I probably would have done the eclipsing binary job anyway.

DeVorkin:

Well getting into limb darkening coefficients of course takes you into atmospheres.

Kron:

Stellar atmospheres.

DeVorkin:

And was this interest generated by your contact with Shane?

Kron:

Yes.

DeVorkin:

I see. I know sometime in the late Ď30ís maybe just a little after your time at Berkeley, a number of the students at Berkeley got together and translated Unsoldís Sternatmospharen.

Kron:

Some of the students were using Unsoldís book but the ones that didnít make up their own minds about that were using Rosseland.

DeVorkin:

Okay, was that you too?

Kron:

Yes. Shane was using Rosseland.[5]

DeVorkin:

Iíve asked you then about the relationships between Lick and Berkeley. I know, though that there were some continuing ill feelings based on the very difficult teaching and research assignments the two staffs had. Was there anything that affected you — anything that you could recall?

Kron:

No. I donít think it affected any student at the time. Of course I wasnít a normal student because I had such remarkable privileges at the Lick Observatory, probably more than any student ever had there before. I had complete entry into the shop and most of the money for instrumentation that year was spent for the photoelectric photometer. In other words I was responsible for spending almost all of the research money that year for new equipment, that kind of money. And I had a lot of time on the 36-inch telescope even for experimental work and Mayall was very much interested in using the photometer on the Crossley. So I had his encouragement. He wanted to see photoelectric development on the Crossley and later on after I began to get results Art Wyse took a deep interest in that. And Wyse and I worked closely together; Wyse formulated the first complete analytical least squares method for solving corrections for eclipsing binary elements, a complete analytical method. And I applied that. My publication in the LICK BULLETIN wasnít my thesis. It was a paper written on the basis of doing it all over again, with Wyseís least square method.

DeVorkin:

I see. That explains the lag of a year or two.

Kron:

Because it was all done over. Of course, the whole method had to be generated and I acted as Wyseís arithmetic assistant on that. He would formulate the equations and the way we went about it was instead of solving the integrals for the different differential coefficients he solved them once and for all and tabulated the results. And then you computed your differential coefficients from tabulated parameters. And this took quite a while. Then later on John Irwin tabulated the coefficients themselves in a paper in the ASTROPHYSICAL JOURNAL. That was the origin of all of the least squares approach to eclipsing binaries. Of course, in the paper in L.O.B. 499 there are probable errors quoted you know. And I didnít get a good hold on the probable errors in the way I did it. I used a method, as a student, for my thesis that was designed by Pannekoek and used by Pannekoek and Elsa van Dean in Holland. I corresponded with Pannekoek and got to be quite a pen pal of his. He was very excited over the accuracy of observations that could lead to a positive result.

DeVorkin:

I know that youíve mentioned him and I didnít realize that you corresponded with him.

Kron:

Yes. He was a splendid person, at least as a correspondent. I never met him personally, I always wish I could.

DeVorkin:

He was somewhat politically on the outs in Holland.

Kron:

Was he? Maybe he was a Nazi.

DeVorkin:

No he was a Communist, I believe (a Marxist).

Kron:

He was?

DeVorkin:

Yes. But you didnít know anything about that?

Kron:

No I didnít know anything about that. I was just a student at the Lick Observatory.

DeVorkin:

Unless you were visited by the F.B.I. later, Iím sure it didnít bother you at all. Iím sure there was nothing wrong with his science. Well this is just something that weíve recently learned. Iíve been interested in Pannekoek because since the turn of the century heís done some excellent work and yet his work is little known.

Kron:

He was one of the great Dutch astronomers.

DeVorkin:

Right. But he never linked up with anyone, he was always at a place where there were no other astronomers, his research didnít continue, and we wanted to know why. Well, at this point though you were getting your degree, your thesis, were you beginning to look for a job, or was there any question that you wouldnít stay?

Kron:

My state of mind was rather curious. The state of mind of a person looking for a job in those days was one in which you looked only at the present and it was depressing to look into the future. To tell the truth I lived only from day to day and for doing my thesis. I had no hopes of any kind, I didnít know what Iíd do. But the three of us, this was Babcock, and Popper and I, all did pretty well. We were very strongly supported by Mr. Wright who sent us on a trip East at Observatory expense to give papers on our thesis problems at the American Philosophical Society and, of all places, the National Academy. I gave mine at the National Academy. That was some real training. And so we all had good thesis material and if I say so myself the three of us, I think, were among the outstanding Ph.D.ís of the year in the country. And so we all got jobs and of course I got mine locally. But I think I might have had a little feeling that since much time and money had been invested in the construction of the photoelectric equipment for the 36-inch that they might want somebody to run it later on. And of course this is what happened.

DeVorkin:

During that time, in the late Ď30ís, especially now that youíve told me that Art Wyse worked on these new techniques, could you discuss him?

Kron:

Oh yes. If Wyse had lived. Letís put it this way, if the war hadnít come Wyse and I would have immediately started to work very closely together and would have gone on probably the two of us supporting each other in the interest in eclipsing binaries, and would have spent much more time on eclipsing binaries than I did because it would have supported each other you see. He was a very brilliant person and I think it would have turned out that he would more or less have directed the effort and I would have done the observing and of course would have worked with him closely but he would have been the top dog I think in this. And I think he would have become director of the Lick Observatory too, later on. There was beginning to be a little bit of rumble that way at the time because everyone knew that Wright would be director only for a couple more years. Had the war not come it seemed unlikely that another very old man, namely J.H. Moore, would have been appointed as director.

DeVorkin:

But Moore was director for a short while.

Kron:

Yes, but only because there was no one else there. You see all the young people had gone. So it was between Wyse and Nick Mayall, either one of those would almost certainly have been the director had the war not come.

DeVorkin:

Let me continue on this particular question now. When you say had the war not come, do you mean the early Ď40s?

Kron:

No, Iím talking about 1939, just about 1939.

DeVorkin:

Was it already too late for the possibility of Trumpler becoming director?

Kron:

He was never considered. Trumpler didnít want it and didnít like the Lick Observatory as an environment in which to work.

DeVorkin:

Why was that?

Kron:

He liked city life. His wife did too. He left and took the appointment in Berkeley on his own, as far as I know. Now I donít know much of what was going on there from direct knowledge at all. I wasnít in a position to get any confidences from any of the older people. But my impression has always been that Trumpler liked teaching, liked Berkeley, and I think this is correct. He went down when he got an opportunity to be on the staff at Berkeley.

DeVorkin:

Thatís quite interesting. That certainly clears up that kind of a question.

Kron:

If itís correct. I think it is because I knew Trumpler pretty well and I know that he didnít like it at Mt. Hamilton because he didnít like living on a mountain top. Of course, Wright didnít like him personally, he wasnít enthusiastic about him put it that way. There wasnít an enthusiastic personal relationship between Wright and Trumpler. But I donít think there was any antagonism.

DeVorkin:

Trumpler had a pretty heavy accent.

Kron:

Very heavy, you know what Swiss accents are like. Zwickyís was like that you know.

DeVorkin:

But could there have been an element there?

Kron:

There could have been, yes. The old guards you know were red blooded Americans and all that.

DeVorkin:

What about some of the other names there, like Hamilton Jeffers and G. Neubauer?

Kron:

Neubauer felt that he was discriminated against because of his foreign connection, but I donít think he was. I think Neubauer just wasnít good enough, because here you had George Paddock who was a good old Irishman who should have gone along well with Moore and Wright. But he was very incapable — he wasnít even mentally solid and he was discriminated against much more than Neubauer.

DeVorkin:

Jeffers was never considered either.

Kron:

Not, no I donít think Jeffers would have wanted it. As far as I know he was never considered, but you see this is all a personal opinion generated in me, in the pre-war era, when the fact of the war changed everything very radically. What with Arty Wyse losing his life and the old guard disappearing completely from the Lick Observatory during that time Mayall, if he had been considered, must have turned it down because when it was evident that war wouldnít last much longer Mayall arranged to see the President Sproul in Los Angeles one time. Sproul used to go back and forth between Los Angeles and Berkeley.

DeVorkin:

No I didnít know that, but thatís an interesting thing.

Kron:

He was very conscious of the necessity of keeping in personal touch with everything that was going on. So he spent part of his time at UCLA and part of his time at Berkeley.

DeVorkin:

Thatís probably why thereís a hail named after Sproul at UCLA.

Kron:

It could be. Thereís one at Berkeley too. And Nick and I were wondering, there were jobs galore you know, especially for scientists.

DeVorkin:

After the war.

Kron:

Well you could see them developing. We could have stayed at Inyokern for example.

DeVorkin:

We donít want to skip over that but letís finish this thought.

Kron:

This thought is important I think because it has a bearing on the future of the Lick Observatory, and the 120-inch telescope. So Nick arranged, this was entirely on his initiation, a meeting between Sproul and Nick and me when Sproul was in Los Angeles. That made it easy because Nick and I were in Pasadena at the time. What we wanted to know was what plans Sproul had for the Lick Observatory, because we could see that there might be other opportunities for jobs and we wanted to be in a position of strength, as far as knowledge was concerned, to know whether we should look for another job or not. And Sproul was extremely friendly and anticipated what we were up to. And he said; ďWell, itís been like a summer resort for friendly old men hasnít it. I think that weíll change this after the war. I think that there will be much more money put into the Lick Observatory and how would you like Donald Shane as director?Ē We were about all that were left on the young staff, Nick and I. Jeff was still there. Art Wyse had lost his life.

DeVorkin:

Was he in the infantry?

Kron:

No. Mr. Wright could see the war coming. He suggested that Mayall and Wyse and I, the only young people on the staff, try to become Naval Reserve Officers. So we all went down to San Francisco and took the medical examination, and thatís as far as Mayall and I got. But Art Wyse went through and got a commission as a Reserve Officer, if you get a commission.

DeVorkin:

So that was voluntary.

Kron:

Entirely voluntary. It was for something to do if and when the war came, you see. But Mayall and I were rejected for various physical reasons. And Art lost his life when he was in a blimp off the East coast. There were two blimps in a nighttime operation that was for the following purpose: they were dropping very large flashlight bombs, and these would penetrate the water and go down to below where they thought a submarine might be. Then theyíd go off and the submarineís silhouette would be projected up through the water. And I suppose that one blimp would drop it and the other blimp would watch, or the blimps were supporting each other some how. And there was a collision between the two blimps and one of those flashlight bombs went off, Everybody in both blimps except one enlisted man lost his life.

DeVorkin:

A straight accident then.

Kron:

A real horror too.

DeVorkin:

May I ask why you and Mayall didnít pass?

Kron:

Well I donít know why Mayall didnít pass but they claimed I couldnít see nor hear well enough to be in the Navy and being underweight and not very healthy looking. (laughter) It was all right. I really didnít want to be an officer.

DeVorkin:

Back to this thing about your meeting with Sproul. When we finish with that weíll go through your war work.

Kron:

Well that really ended the interview. Nick and I decided we would come back to the Lick Observatory. We both enthusiastically accepted the possibility that Shane would be the Director.

DeVorkin:

George Paddock was involved somehow?

Kron:

Oh, I was making a point for the fact that the only people whose opinions really counted as far as Sproul was concerned were Mayall and I because the only other people who would be there were Paddock who was practically mentally incompetent, and Neubauer, who felt that he was being discriminated against. But he really wasnít a very good astronomer. He could run a spectrograph, but he didnít have any ideas. And then H. Jeffers whose work was all cut out for him and who I think had no interest in anything except measuring double stars, and I think that probably Sproul knew that. And thatís all. That was the entire staff. So we had the interview with Sproul, and then Sproul mentioned something about hoping for a very large telescope.

DeVorkin:

He must have been talking to Shane then by that time.

Kron:

He must have been, sure. Of course he and Shane knew each other very well. He was quite a man, Sproul.

DeVorkin:

Does that finish that particular interview?

Kron:

Yes, that finishes that particular interview with Sproul. It was a very friendly interview.

DeVorkin:

Letís move back then to approximately 1940 then and move into the war years. You continued to do other light curve work. You had followed the eclipse of Zeta Aurigae.

Kron:

Yes thatís right and I worked on one called AR Lacertae and had lots of observations. And I had started work on what was probably the climax of my career in the eclipsing variable business, HD 193576, that was a dandy, the Wolf-Rayet star. Olin Wilson at Mt. Wilson got me on to that. He was an old friend. He and Whitford and I palled around during the summer assistant days when we were in Pasadena with Stebbins you see. Olin Wilson and I still are good friends. I always go to see him when Iím in Pasadena and were rough contemporaries, Olinís a little older than I am. He and Whitford are about the same age, a couple of years older than I am.

DeVorkin:

He might be a good person to talk to.

Kron:

Olin Wilson! Heís great. Heíd be a darn good person to talk to. He could give you all kinds of ancient and modern information about conditions at the Mt. Wilson Observatory and the relationship with Cal Tech. He was in on all of it. He was just the right age. It was during that time when the old guard was going out and a lot of new people were coming in and he spanned that just as Mayall and I did at Lick. And those are interesting periods. You see the thing was that the people of our age were born just before the first World War and there arenít very many of us.

DeVorkin:

Why?

Kron:

Well the population was down, the big population increase probably took place after the first World War, just as there was one after the second World War you know. There were very few people of our age in astronomy.

DeVorkin:

During the Ď30ís?

Kron:

During the Ď30ís.

DeVorkin:

You continued to work on it and this particular star the Wolf Rayet Star, RD 193576, you wrote about in 1943[6] indicating that your original work on it was interrupted by the war but you were able to return to it temporarily in May of 1942. Was this on a furlough or something?

Kron:

On a vacation, I came back to Lick and worked on it.

DeVorkin:

Did you work with your wife at that time?

Kron:

Well she wasnít my wife at that time.

DeVorkin:

Well shall we talk about how you met her or should we do the war work first?

Kron:

Well they are closely related.

DeVorkin:

Okay, Iíll let you guide.

Kron:

I probably wouldnít have met her if it hadnít been for the war work. When Britain was in its terrible trouble, the development of microwave radar was undertaken in this country to help the night fighters, you see. They wanted compact accurate radar equipment that could be put in a small airplane. And the discovery of the magnetron in England made this a possibility. But the development threatened to be rather difficult and so this was undertaken at the Massachusetts Institute of Technology. Whitford was siphoned out of astronomy rather early and he got me into it. So in May, 1940, I went to Boston.

DeVorkin:

That early?

Kron:

That early, yes. I worked on microwave radar. I worked in the indicator section and did development work in the displays, the cathode ray tube displays. At the end of that year my health began to fail, partly because of the climate. Finally I got to the point where I had one cold after another. I was never free of something like that, so I went back to Lick for a couple of weeks and installed the electronic drive in the 36-inch. I had gone through all the designs for this and the mechanical parts had been made in the shop and all of this was done when I got back so I put it together and made it work. Meanwhile Horace Babcock had also gotten tired of the awful weather in Boston. I donít know of any other way of describing it, it was just horrible. We lived in Boston and worked in Cambridge, right across the Charles River. Later we found out about the rocket project at Cal Tech and so Horace was the entering wedge there and Mayall, Horace and I, and Olin Wilson, all joined that Rocket Project. I think Mayall was on it or he was closely associated with it.

DeVorkin:

Mayall was with NRL.

Kron:

Thatís right. He wasnít exactly on our project but I saw him every once in a while. But Horace was and Olin Wilson and I worked together. So I joined the project and went to Pasadena to live. When I was in Boston the observatory people were very gracious in inviting me to all kinds of things that they did: dances, and picnics and conferences and colloquia. And on a picnic at Oak Ridge I met Katherine for the first time. But only for a moment. I was just introduced to her and that was it. She was just there. She was a student, she was a Radcliff student at the observatory. Meanwhile however she had gotten an assistantship at the Lick Observatory.

DeVorkin:

Completely independent of you?

Kron:

Completely independent of me. And shortly after I went back temporarily to install that drive she arrived as an assistant. And so I got to know her there, but it was only for a few weeks. And I also got to know Carl Wirtamen who had come as an assistant. He and I became very friendly.

DeVorkin:

He was definitely an assistant and not a student?

Kron:

Yes, definitely an assistant.

DeVorkin:

Where were his student days?

Kron:

At the University of Virginia.

DeVorkin:

So he worked with Vyssotsky?

Kron:

Yes, he knew Vyssotsky and the man in charge was S.A. Mitchell. Of course I didnít expect to stay, I was already in war work and I would either have gone back to M.I.T. and probably have died of tuberculosis or somethingÖ

DeVorkin:

So you went back to Lick only temporarily?

Kron:

It was just a temporary escape and also the excuse was to finish the drive for the 36-inch. There wasnít any real need for that, it was working with the weight drive. But it was a good excuse for me to go back.

DeVorkin:

What do you think ever happened to the weight drive, did it just get put in the old shop?

Kron:

It was dismantled and I think the clock was left in the mounting wasnít it, the big clock?

DeVorkin:

I donít know, I never looked.

Kron:

It was rather a pretty looking thing.

DeVorkin:

The governor you mean?

Kron:

Yes.

DeVorkin:

That would be the thing to save.

Kron:

But the weights were dismantled and the parts that could have been dangerous were dismantled.

DeVorkin:

Well you were working there then.

Kron:

I was there temporarily and I knew it would have to be temporary, but meanwhile I had corresponded with Horace Babcock.

DeVorkin:

Could I ask why it had to be. In other words, you were a civilian?

Kron:

I felt I had to go back and do some kind of war work.

DeVorkin:

This was your personal decision?

Kron:

Yes. Once you get into it, itís hard to get out. Of course December 7th had taken place while I was in Boston actually. And that gives you a feeling. I would have been inducted somehow anyway. In 1940 I was 27 years old and they were taking people in their late 30ís in the Army at the time. It turned out to be a mistake but they were doing it. So you have that little extra drive because of that. But there was also a lot of interesting work to be done.

DeVorkin:

You heard about the Rocket Project.

Kron:

Through Horace Babcock, I didnít know it was a rocket project.

DeVorkin:

What did he say?

Kron:

All he said was that there was a project going on at Cal Tech and why didnít I try to get in there. And we were very close friends, we still are. And so I went down there for an interview and they were looking for more people and Olin Wilson was very enthusiastic about having me there. And so I got the job and was assigned to work with Olin Wilson. And shortly after that both Wirtanen and Katherine got the urge to do something a little more productive. The Lick Observatory was a terrible place at the time. Paddock was there, who as I say was practically incompetent, and Mr. Wright who was in his 70s, and Doc Moore who was also 70, and a few hangers on: Mr. Cosh, the instrument maker was there, all elderly people, none of them very active, nothing to do that really was important. And it was no place for young people. So both Wirt and Katherine went after me to try to get them in down there, you see, when I got in so easily. So I got the both of them in. And Wirt went out to Eaton Canyon and worked on propellants.

DeVorkin:

Where?

Kron:

Eaton Canyon. Thatís where the powder presses were and the propellants were made.

DeVorkin:

In the L.A. area?

Kron:

Northern Pasadena. And I became part of what was known as the Accuracy committee. We were supposed to make rockets go straight and we never did it. Katherine went into what was called Foladareís Follies. Joe Foladare ran the editorial department and he had a number of girls there who helped with the editorial work in getting the equivalent of papers for the reports on the results and the progress made by the project. And we stayed there until the end of the war, more or less, associated with that project.

DeVorkin:

You said you went out to Inyokern?

Kron:

Yes. That was a Cal Tech project in its early days. And so when I first went out there I went out as an employee of Cal Tech and a civilian. Well I was always a civilian. Then later on when the Navy began to form an idea for making a major base out of that area, we were transferred there, if we agreed. Nobody was forced to do anything. But I liked it there and wanted to continue working and if you wanted to stay there you had to take a job as a Navy civil servant and I did.

DeVorkin:

You did stay.

Kron:

Oh yes I stayed until the end of the war.

DeVorkin:

There were a number of astronomers out there.

Kron:

Yes.

DeVorkin:

Who were some of the other people?

Kron:

Well, Franklin Roach showed up once in a while, Elvey was there. Elvey was in charge of quite a large section later on in the war, Christian Elvey. Horace was working on rights for aiming forward firing rockets but he wasnít out there, he came up for tests quite often. I saw a lot of him. Dorrit Hoffleit was there.

DeVorkin:

Did you find that the astronomers were doing a wide range of different things?

Kron:

Thatís right, not necessarily very closely associated with astronomy at all. Of course I was doing internal ballistics in the early part and external ballistics of forward firing rockets. This required some simple arithmetic that was remotely connected with astronomy. And later on I was with a group that, that was, I think, probably a red herring to disguise the fact that the high explosive lenses were being made in a remote area of the Inyokern Project for the plutonium bomb.

DeVorkin:

These were the shaped charges?

Kron:

Shaped charges, yes. An assembly of shaped charges that compressed the tamper.

DeVorkin:

Were you aware that there was something peculiar?

Kron:

Oh sure, I knew what was going on.

DeVorkin:

How did you find out, how did your awareness grow about what was going on? Get it from the beginning, if you can.

Kron:

Well the first thing that happened is that we became aware that there was something going on that was related to the Manhattan Project.

DeVorkin:

When was this about?

Kron:

Iím not even sure. I donít really know. The time then didnít flow uniformly, it flowed depending on what was going on as far as the war was concerned. Sometimes it went rather fast and other times it didnít. When was the war over? It was in Ď45. Well this is probably in Ď44, probably very early in 1944. And several things happened. One is that a friend of mine, who I had met on the project in Pasadena, when we were travelling back to Pasadena one time. And he said: ďYou know they claim they are working on a special kind of high explosive bomb out there.Ē And we knew that they were working with shaped charges. And he said: ďYou know what goes on in the middle of that thing must be very remarkable.Ē And we mused a little about that. And then as it happened, there was organized a project for dropping these big bombs, B29ís would come in from a place that was called Kingman and I was assigned to measure the drop time of these enormous bombs I had to go up, and did a lot of flying in B29ís and we devised a little radio thing called informers that would be dropped with the, bomb. And a trailer gadget on the ground would measure and observe the radio signals with timing pulses on them from the beginning release of the bomb to the time it was all destroyed when it hit. This would give the time to within, I guess, a few hundredths of a second, the drop time. They were interested in that. We didnít know why.

DeVorkin:

We were in the middle of talking about your work dropping bombs to determine the time of flight.

Kron:

Thatís right.

DeVorkin:

Why was this a necessity?

Kron:

I never did find out. I donít know why they wanted to know it. But I thought that one reason was that had nothing to do with science at all. I think that this is probably what was going on: they wanted the crews to have experience dropping the bomb. They wanted to know something about the external ballistics of the bombs. They used it I think as a red herring project to hide the sensitive work that was done on the lenses.

DeVorkin:

You knew these bombs had the shaped charges in them?

Kron:

Yes. We knew that they were going to be used with shaped charges but at the time none of us knew what was inside.

DeVorkin:

But you knew it was something peculiar?

Kron:

But later on I was let in on the secret and visited W47 and Kingman in New Mexico.

DeVorkin:

How were you let in on the secret?

Kron:

I had done some electronic work on this thing they called the informer. The original design had come from Los Alamos and I made improvements on it and I think they decided that I would be useful to have some interchange of ideas. And the only way to bring those about was that I had to be taken in on the secret. I visited the places where they stored the dummy bombs and then I visited at Los Alamos where they were making the real ones and talked to people there. I saw Shane there by the way. He was personnel manager at Los Alamos.

DeVorkin:

Iíll be!

Kron:

He hated it.

DeVorkin:

Why did he hate it?

Kron:

There was a general there, I canít remember his name, who had the Army responsibility and he and Shane didnít get along at all. Shane had to force himself to get along with him and Shane resigned the day after the war was over.

DeVorkin:

He had no intention of staying?

Kron:

No intentions of staying whatsoever.

DeVorkin:

It gave him good administrative experience.

Kron:

Yes, it probably gave him wonderful administrative experience because it was all up hill. A very difficult job.

DeVorkin:

In dealing with the military?

Kron:

Also dealing with the employees there. They had a great deal of trouble with the people who did the mechanical work on the critical parts. These people had to be kept happy and they knew their strength, you see. They were responsible for making the actual things that were going to be dropped. Although they didnít know as much as I did about what they were working on, they did know how vital it was and what a terribly pressing thing it was. So they were always making trouble with strikes and demands for salary raises and improvements in this, and improvements in that. It was a terrible situation.

DeVorkin:

Was this a unionized situation?

Kron:

It was all local. No I donít think it was a union at all. It was local organization based on their sense of how much they were needed.

DeVorkin:

Were there ringleaders?

Kron:

Yes I think there were. I donít know anything about the details but there couldnít have been any outside communications because Los Alamos was isolated. It may have well been in a cave with just one iron door someplace as far as access was concerned. People had to stay there all the time as far as I know.

DeVorkin:

Shane may have already discussed this in the interview with him.

Kron:

It would be hard for him not to I think because it was a terrible time of his life in his career.

DeVorkin:

I think Iíd better check though, to see, because that is extremely important.

Kron:

Indeed it is.

DeVorkin:

So you were let in on all of this?

Kron:

I knew what was going on, yes.

DeVorkin:

Did you realize the potential of the bomb?

Kron:

Oh sure.

DeVorkin:

How did you feel about it?

Kron:

I was happy as could be.

DeVorkin:

You can be frank.

Kron:

If I can say so. There wasnít anything I wanted more than to see the Japanese just knocked out completely.

DeVorkin:

Okay weíve been talking about how the Japanese were regarded. What was your feeling about this.

Kron:

My feeling was that we had arrived at the point where it was obvious that we were pushing the Japanese back toward Japan. It was also pretty obvious, at least we all thought it was, that the thing could never be finished without an invasion of Japan. And we all felt that this was going to be one of the most awful experiences that probably any country had ever had in the world. And so none of us at the time, and associated with this project, had any moral compunction about dropping the bomb. Except a few people, I think, some of whom were at Los Alamos, had scruples about this and most of us didnít even understand that.

DeVorkin:

Understand their scruples?

Kron:

Yes, how people could feel, under the circumstances, that the bomb shouldnít be used.

DeVorkin:

Were you surprised when you saw what the bomb did do?

Kron:

Not particularly — the reason is that I knew both Wallace and Bob Brode. Iím not sure Wallace ever worked at Los Alamos, but Bob Brode worked at Los Alamos practically from the start of it. And he was what you might call my contact. I think he was the one who arranged for my trip to Los Alamos. He was in cosmic ray research during the hot period at the University of California at Berkeley. He was one of the triplets. And he and Wallace were identical twins and the third Brode of the triplets of course couldnít be identical — it isnít the way it works. He was a chemist and died relatively young. Wallace was with the Bureau of Standards I think and Bob was in Berkeley before he went to Los Alamos, of course he was still associated with Berkeley at Los Alamos. And he came through Inyokern several times while we were in this bomb dropping phase with the B29ís. I was no longer doing rocket work, I was completely devoted to this problem. And he dropped through right after the test shot at White Sands and described it. He thought Iíd be interested as an astronomer. He knew the temperature and they had spectra and it was an astronomical problem really because what they were looking at were conditions that were a little like the conditions deep inside a star. He said the temperature they estimated to be 70 million degrees at the time they were able to measure early in the development of the nuclear reaction. And of course the spectra were fantastic. So we had a long talk about that, but then I knew of course, what it would do because he described what it did to the area there. It vaporized the whole tower, so you could tell it was going to be quite an event. And of course that wasnít the one we were working with in Inyokern. That what they called the ďthin man.Ē It was a primitive thing that was built to get the quickest possible application of the thing.

DeVorkin:

Which one were you working on?

Kron:

I didnít really work on any of them, but the ones that we dropped were all dummies, except that some were full of TNT, just a solid chunk of TNT. The ones that had the lenses, the plutonium bomb, was called the fat man. It was a big bulbous thing whereas the first one was built around either a 75 millimeter or 5 inch cannon and the two pieces of U235 were assembled in the barrel of this thing. I donít know what the size of the gun was. I saw one at W47 and it looked to me like a 75 millimeter. Since then Iíve had the feeling it must have been bigger, because it usually takes about a kilogram of the stuff — maybe you could put a kilogram in a 75 millimeter.

DeVorkin:

Well what were your plans after your trip to Los Alamos and your continued work at Inyokern?

Kron:

We certainly knew that it wouldnít last much longer.

DeVorkin:

Did you start getting a taste for what people would call ďbig science.Ē In other words team research.

Kron:

No. I wanted to go back to Lick because I had some ideas then and I wanted to work them up. What had been happening all this time about observing the Wolf-Rayet binary is that Wirt and Katherine and I would spend a week or two of our vacations at Lick and observe in series. So we kept it going pretty well during the war and by the end of the war we had a lot of observations. And the exciting thing was the fact that one of the two eclipses lasted much longer than the other, very much longer. And this was brought out by our observations. That was our discovery about the star. So I wanted to get to the matter to see what could be done about orbital elements with such a bizarre light curve. We analyzed the light curve as if it were two different stars. We worked with one eclipse and got elements and then worked with the other eclipse and got elements and then finally we used the limb darkening tables in a way they were never intended to be used, in order to demonstrate that one explanation is that there was either a shell or a ring around one of the stars.

DeVorkin:

I recall that in your paper in 1950[7] with your wife. She still went under the name Katherine Gordon?

Kron:

Thatís her pen name. She still does.

DeVorkin:

That was on the structure of the Wolf-Rayet star V444 Cygni.

Kron:

Thatís HD193576.

DeVorkin:

Oh itís the same one.

Kron:

Yes. It didnít get its variable star number until later on when the variable catalogue people got active again.

DeVorkin:

I see. Well this paper was not published until 1950 and this was based upon work between 43 and 46 that you continued during the war, and you were working with red sensitive cells at that time. Had you had any contact with John Hall who had done something along those lines?

Kron:

Oh sure, I knew Hall quite well through Stebbins and Whitford because either Stebbins or Whitford, Iím never sure which or both, wanted to develop multiple color photometry and this turned out to be six-color photometry. And in order to do this they had to use an S1 photocell and it was John Hall who had discovered how to use infrared sensitive photo emissive cells by refrigeration with dry ice. And Whitford worked out a design for a photometer and I copied it. I tried to improve it but the design wasnít very good to start with. Itís very hard to do because it should be really hermetically sealed and I didnít solve the problems of making a good photometer receiver until after I started doing high vacuum work on the electronic camera.

DeVorkin:

Thatís interesting. Letís go back to just after the war. You were coming back to continue work on the Wolf-Rayet stars and it seems to me though some of your first papers right after the war, especially AP J 103, 1946, page 326 dealt more with the photo multiplier tubes — the new 1P21.

Kron:

Thatís right.

DeVorkin:

How did you learn about the photo multiplier, was this while you were in the war?

Kron:

Letís go back to the guider for the 200 inch. Whitford and I, quite naturally, designed our guider around the use of a diode photocell. Now the guider had a shutter in it that was driven by a synchronous motor. And photocells have an anode that is just a wire that is supported only at one end. And theyíre very microphonic. We found out when we were using this that the vibration from the motor created such a microphonic noise level that the device was bound to be totally useless.

DeVorkin:

But you didnít do anything at the time?

Kron:

There wasnít anything we could do about it except that Stebbins knew V. Zworykin personally. I donít know how, I never learned where Stebbins got to know Zworykin. And Stebbins knew that Zworykin was working on some kind of a device at RCA and so he wrote to Zworykin. We knew that it was a multiplier, I think we knew how it worked. It was magnetically focused by the way. And Stebbins said heíd write. Of course Whitford and I realized this would be totally non-microphonic because amplification had nothing to do with anything that could create a microphonic condition. So Stebbins wrote to Zworykin and sure enough Zworykin sent a laboratory constructed magnetically focused photomultiplier. It had an S1 surface, it turned out. And thatís what we used in that guider, it actually worked. That made it work. So I knew about photo multipliers. And then not very long before the war started Whitford got a diode photocell that had the S4 surface, the alloy antimony-cesium surface. Thatís the blue sensitive one. Thatís the one the 1P21 has. And he said that this is the most remarkable thing ever worked with and he sent it to me to try. I think he just mailed it. It was an ordinary photocell. And I tried it and by George it was at least as good as my fine Kunz cell. And it was a vacuum cell. Its construction didnít cater to super-insulation or anything. It was really marvelous. So I was introduced to the S4 surface and I thought to myself if we could just get a multiplier with one of these surfaces photoelectric photometry would be revolutionized.

DeVorkin:

Did you show this to anybody else at Lick at the time?

Kron:

No, I didnít show the cell to anyone because it wasnít mine and I didnít know how to get one. It was, a laboratory product from RCA. And I didnít think it would do any good and the war fever was beginning to be felt, and very soon after that the 93lA appeared. And Stebbins got me a very small grant I think $300, from the American Philosophical Society, to develop the photo multiplier as an astronomical light detector.

DeVorkin:

Oh it would be marvelous to see the written grant proposal on that.

Kron:

Yes. Itís probably at the American Philosophical Society. And before the war I think I bought one or two 931Aís, they didnít cost much, $12 or $15, something like that.

DeVorkin:

Right. People always looked at them as a poor manís 1P21.

Kron:

Well theyíre no good.

DeVorkin:

Were they the same design?

Kron:

They were the same design and I think the 1P21 was built every once in a while and I think they just simply got a good vacuum in them thatís all. They got the 1P21ís for a while by selection. Later on you could see that the insulator inside it said ď1P21Ē, so they knew they were making 1P21ís later on. They cost $50, that seemed like an enormous fortune at the time. I canít remember now whether 1P21ís were available when I got that grant or not. But I got totally immmersed in the war by then. But near the war I still had this money and while I was still at Inyokern I no longer had enough to do to keep me fully occupied, the rocket business at the time was rather over. We had had success in the Pacific and the rockets werenít used much. The war was over, in Europe anyway. So there really wasnít much to do. And I began to work on DC amplifier design and I bought some 1P21ís and I also got the Inyokern project to buy some because there were some applications there and I went through the collection of mine and the ones that the project had bought and took a couple of the best ones back to Lick.

DeVorkin:

Thatís another interesting thing. You did have funding contacts with the military at Inyokern.

Kron:

Oh yes, oh sure, we had to be able to buy equipment.

DeVorkin:

And so were they interested in image detection?

Kron:

No. But they were interested in such things as photoelectrically operated shutters. For example one of the things they wanted to do was to have a series of cameras and as a missile went through the air they wanted the camera to turn on when it was in the field of view. And one camera to turn on after another. And the one way to do that was to have a photoelectric device in each camera that would trip the camera when it saw the projectile coming. And so I did some photoelectric work there. And I did other electronic work I was in charge of something called the Special Devices Group and when anyone needed some bizarre piece of equipment they appealed to us. They told us what they wanted it to do and we were supposed to design it and build it. We had an optical shop, a high vacuum laboratory, a machine shop, a plating laboratory and I was also in charge of the computing group there. So I had something a little over thirty people working in my direction.

DeVorkin:

The computers were all manual?

Kron:

Oh yes, sure there werenít any electronic computers then. At least we didnít have any. What they did was to reduce the range data, the range data would be brought in at the end of the day and would be processed the next morning by the computing team.

DeVorkin:

Was that what Dorrit Hoffleit was involved in?

Kron:

No she wasnít. I donít know what she was doing.

DeVorkin:

So then you certainly were very well aware of multipliers all the way through.

Kron:

Oh yes. Because you see the first from that first magnetically focused one, Whitford and I were both on the ďKVĒ about multipliers.

DeVorkin:

You were on the what?

Kron:

On the ďqui viveĒ. On the hair-trigger sort of. My advantage came over everybody else when the war was over: I had an amplifier design that I made during the war. It was cheating of course. And I had 1P21ís. I had two of them. And shortly after I got back to Lick I arranged for Stebbins to come to Lick. Stebbins had lost his research associateship, all of them had been lost, they terminated the research associateship at Mount Wilson.

DeVorkin:

Did he ever talk about why it happened. I was going to ask you this specific question. He bought a house and everything.

Kron:

He bought a house and everything. He was very badly upset by that emotionally, and he was quite angry about it. But there were only three of them, Eddington, Henry Norris Russell and Stebbins, and they were all terminated. But Stebbins was the only one who used it. And they carried salaries and Stebbins was actually collecting a salary and he expected to keep on. And this would contribute to his support. So they really pushed the rug out from under him, especially with that house. But the real estate values were going up so rapidly, he sold the house at a profit, so Iíve never been terribly sorry for him, or sympathetic about the house.

DeVorkin:

Did he ever talk to you as to why it was terminated?

Kron:

He thought that they were being cast off as old fogies, but it was a genuine necessary economy at the time. Iím quite sure of that. I donít think there was any personal thing involved at all. But I think the way it was done was rather brutal. They werenít given any advance notice. They didnít give Stebbins any compensation of any kind, like keeping him on another year or so because he had the house there or anything like that. So he was I think justifiably upset. But I think he was upset for the wrong reason. He was upset because he felt that they were being just dumped. They werenít. They really had to economize at that time. So I got him a research associateship at the Lick Observatory.

DeVorkin:

You were responsible for that?

Kron:

Yes. I arranged it with Shane. Shane gave it to him.

DeVorkin:

But there was no difficulty convincing Shane?

Kron:

No. None whatever.

DeVorkin:

You had the money?

Kron:

Yes.

DeVorkin:

How did you have the money?

Kron:

The Lick Observatory was a campus of the University of California and Shane knew Sproul extremely well. So Sproul had decided to build up the Lick Observatory after the war. So this was part of that, Stebbins was brought in. Henry Norris Russell was too. I got Henry Norris Russell a summer appointment there, through Shane of course. It was my recommendation.

DeVorkin:

That must have been very interesting. This is a question I had in the back of my mind, during the period of the late Ď30ís when you had been getting into double star work, especially eclipsing binary work, Russell of course had the very early general methods for binary star reduction but by the late Ď30ís there were numerous efforts, Kopal and others, to make these methods more rigorous and to work on them. Were you aware of Russellís early work at that time?

Kron:

Oh yes. I did all of my work based strictly on Russellís work. I used his tabulations of the alpha function, use of the chi function and things like that, that he had devised, methods that he had devised. They were very ingenious.

DeVorkin:

So you certainly felt that his presence would be quite valuable?

Kron:

Oh yes. He was a very interesting person to have there, especially for me.

DeVorkin:

What was the atmosphere like when you got back to Lick? Did Stebbins and Russell come directly soon, or was there a period of time before they came?

Kron:

Stebbins came, after a little period of time. I think Russell came very soon. Katherine and I had been married just a short time and we both got to know him and Mrs. Russell very well. Stebbins came in 1948 and stayed until 1958. He was there for ten years. And during all that time I worked very closely with Stebbins, although not exclusively. I did some work on my own initiative. I felt highly obliged to work directly with Stebbins, I acted as his night assistant, I designed equipment for his use, I converted the Crossley to photoelectric work because he wanted to do six color photometry. I devised photometers based on miniature photocells. No infrared multiplier became available until Lallemand started to produce his laboratory ones. So we had to continue using photocells up until the time that Lallemand multipliers became available. So I worked very actively in the refinement of infrared sensitive cells. So we had to use photocells with S1 surfaces, and I worked very hard to refine the methods for that by putting them in vacuum tight containers and refrigerating the whole thing — the grid resistor, the photocells, and the amplifying tube — using miniaturized components so that the distributed capacity was reduced to a minimum. But the photometer I finally built was about this big around and that long; the receiver, the light sensitive unit, a little tiny thing. It was just in a little box; they worked very well. And I developed feedback methods to artificially nullify some of the input capacity which allowed us to use higher input resistors and improve the signal to noise ratio. And then all of a sudden Lallemand multipliers came along and wiped it all out. I got to know Lallemand very early in the game and had some of the first Lallemand multipliers. I have all of this in the house. I have the old quartz Kunz cell, some of Lallemandís multipliers here, and some of these little old receivers I made. Iíve got a regular museum.

DeVorkin:

You were talking about how Lallemandís tube replaced yours, and then the fact that you still have all of that instrumentation here in the attic.

Kron:

I donít have all of it but have generous samples. Itís all out of date you see, nobody uses equipment like this anymore.

DeVorkin:

Well Iím very happy to hear that itís still here because when people donít use equipment sometimes they destroy or reuse it.

Kron:

That is why itís here. I was afraid that would happen, especially with the Kunz cell, which of course is getting to be almost ancient history now and I was afraid this would have been discarded. I brought it with me when I left the Lick Observatory. Iím sure no one there would mind.

DeVorkin:

Well no one knew about it. Your son, Richard, found your DC amplifier, I believe it was, that you built at Berkeley. Did he mention this to you?

Kron:

No, but I know that there was one there, there were several there as a matter of fact. But I think that some of them were probably discarded. I built one for Shane for a microphotometer while I was a student there. And then I built one for the 12-inch reflector later on after I was up at Lick, so they could do a student photoelectric work with the 12-inch.

DeVorkin:

I remember seeing, in the mid Ď60ís, in one of your rooms many photometer heads of varying designs, is this the collection you have here, part of it at least?

Kron:

Yes, these all have balsa cold boxes. Yes thatís probably what I have here. They were obsolete then in the 60ís because we were using nothing but multipliers by then.

DeVorkin:

Letís start this right off then with a very important part of your life. How you came to meet Katherine Gordon and how your courtship progressed.

Kron:

Well it didnít progress at Lick, it progressed at Inyokern and Pasadena. So that by the time that we came back to Lick we knew each other quite well. It wasnít really a courtship at all, we worked together during the war and got to know each other well enough to realize that we were emotionally compatible, I guess, you might put it. And it would be a good idea to keep the team going. So thatís what we did.

DeVorkin:

You entered on research work and that sort of thing, but were there any incidents that are memorable or significant that should be recorded?

Kron:

I donít think so. I think everything went smoothly and it turned out well I think.

DeVorkin:

Was there some question as to the type of research that she wanted to do or whether she wanted to continue research. She certainly did, didnít she?

Kron:

She wanted to continue and of course having been a Vassar graduate was really on the outside looking in.

DeVorkin:

She was a Vassar graduate, but you mentioned that she was at Radcliff?

Kron:

Yes, she was doing graduate work there. But as she pointed out unless you were working for a Ph.D. and had some kind of a scholarship you didnít count at Harvard and that was her situation. And she wanted to get into research work but couldnít see how to do it and of course at Lick if she married an astronomer there, why this would solve the problem for her.

DeVorkin:

Do you think thatís it?

Kron:

Oh, I think thereís more to it than that.

DeVorkin:

Maybe we should ask her.

Kron:

Maybe youíd better.

DeVorkin:

So then you were married. Where were you married?

Kron:

In Pasadena, most of our friends were there you see, because we made a lot of friends during the war, mutual friends during the war.

DeVorkin:

You mentioned Fritz Zwicky, is this when you came to know him?

Kron:

Yes I got to know Zwicky during the war.

DeVorkin:

And who else?

Kron:

Olin Wilson and of course, Horace Babcock, she got to know him during the war. And people like Willy Fowler and a man named Cal Matthew with whom we worked during the war. He was in charge of our shop at Inyokern but became quite wealthy with real estate ventures after the war. And some people named Coke — the girl at the time was a secretary at the Kellogg Laboratory. Virginia Coke. And Charlie Robinson who she married later on. I sometimes say that there was a group of about five or six of us and nobody knew exactly who would marry whom. But we were all pretty sure that there would be some weddings sometime, either right after the war or late in the war. Virginia Coke married Charlie Robinson, we still see them, when we go to California and Wirt, Carl Wirtamen, married a girl who we met on the project down there, Edie, I canít think of her maiden name now. So it all got straightened out.

DeVorkin:

You mentioned that Lick pretty much stopped active research during the war. With your contacts in Pasadena did you see a similar situation there at Mt. Wilson?

Kron:

I really canít say. I donít know. I know that Olin Wilson didnít do any astronomy at all. He devoted himself completely to work on the project in Pasadena. He never went to Inyokern by the way. Of course it would have been possible for him to have done observing during free periods. As a matter of fact Iím quite sure that later on it might not even have been possible. Olin married a girl from the project too and we took our two lady friends up to Mt. Wilson one night, but there wasnít anyone there at all. We showed them the telescope and the living quarters and there wasnít a soul there. Olin had keys for everything and everything was vacant.

DeVorkin:

I know that Hubble was at Aberdeen during the war but Baade was around.

Kron:

Walter Baade was there and Baade used the 100-inch for a while. You know he resolved the red giants in M 31.

DeVorkin:

Did you have contact with Baade at all?

Kron:

Oh yes. Katherine and I knew Baade very well.

DeVorkin:

Did you know him well enough to find out how he felt about being under mild house arrest and that sort of thing.

Kron:

Yes, I found out he didnít like it at all.

DeVorkin:

Could you give me some recollections of this?

Kron:

Well he felt quite emotionally upset over this. After all he was Jewish you know and he felt that if anybody shouldnít be suspected of subversive activities it should have been a person like himself.

DeVorkin:

He was Jewish? I didnít know that.

Kron:

Oh yes. He and Minkowski were both Jewish. And why he should have been under any kind of restriction was unknown. Of course it was a very gentle restriction. Iím pretty sure, if you put yourself in the place of the people who were responsible for these things you can see that they canít let one person off Scott free, if they have to put restrictions on someone else. So suppose there was some other German, non-citizen, in the region who might be dangerous. Theyíd have to be pretty tough on a person like that. Well hereís Baade, what are they going to do with him? Well what they do is to do something, as long as it doesnít interfere with his work and thatís what they did. But I donít know what it was, it wasnít a house arrest.

DeVorkin:

Was it a travel restriction?

Kron:

Yes. I think it was a travel restriction. But who would have wanted to travel anyway, especially Baade, he never travelled anyway. He didnít go anywhere.

DeVorkin:

Well he had use of the 100-inch and the rumor is that Americans felt kind of jealous of this.

Kron:

I never heard anything. I was there during that time and I didnít hear anything about that.

DeVorkin:

So as far as his relationship with the people at Santa Barbara Street there was no deterioration, or change.

Kron:

Of course Iím not an authority but ask Olin Wilson, heíd know. But I didnít notice it, Baade never said anything about that. He said things about what he called a curfew. You could see that he was a little bitter about that. But I think it was largely a matter of an emotional thing and not a physical thing. It didnít interfere with anything he wanted to do.

DeVorkin:

Were you in contact with him directly during the time that he made the resolution and came out with his Populations.

Kron:

No. At that time we were all immersed in work in Pasadena. The Population I, Population II concept you mean? No I wasnít in direct connection with him.

DeVorkin:

So you didnít talk, to him about it.

Kron:

No. But Ií was in direct contact with him and to some extent worked with him when he found that the factor of 2 in the distance scale.

DeVorkin:

This was later in the early Ď50ís?

Kron:

Yes.

DeVorkin:

Weíll reserve that. Donít let me forget that. Well the war was over for you, you were back at Lick, were you married by this time?

Kron:

No, not quite.

DeVorkin:

So you went back, to Pasadena, even though you were up at Lick, for the marriage?

Kron:

Yes, we went down there for that because we didnít know where else to have it that would be completely impersonal.

DeVorkin:

Why did it have to be impersonal?

Kron:

Well, our two families were so very different for one thing. It couldnít be in Milwaukee, Katherine wouldnít have wanted to be married there. Katherine comes from a very wealthy family and she didnít want to be married in New York City because it would be sort of a debutant thing with bridesmaids and all kinds of jazz. And we both decided that we wanted to be married where most of our mutual friends were. And since they were mostly made in Pasadena, you see, thatís where it was.

DeVorkin:

Did your mutual families show up?

Kron:

Oh yes, both families showed up.

DeVorkin:

There was no problem there?

Kron:

Oh no.

DeVorkin:

A neutral territory is all right.

Kron:

Well there wasnít any antagonism, it was just incompatibility thatís all.

DeVorkin:

Thatís interesting. Letís go to Lick and the post war years. Certainly Sproulís promises paid off but I understand it was a long hard fight for that telescope. When did things begin?

Kron:

Right after the war. I donít know how it was initiated. I wouldnít be surprised if Sproul initiated it through the Regents as part of his program to expand the Lick Observatory. But I donít know for sure, Shane would know all the details of that. But it depended on getting a special grant from the State Legislature. And the problem lay in the enormous inflation of the cost of equipment of that kind that took place after the war. So whenever a price was given, and the State Legislature would approve of it, as time went on it would turn out that this wasnít near enough to buy the telescope. This was during the design period you see, nothing had been bought, nothing had been built, but Bill Baustian was there with a couple of draftsmen, one of whom was Boesgaard who is now in Honolulu. And Shane began to worry very much about whether or not there was going to be a cooling off in the State. Legislature and whether theyíd get impatient about this. And at one point he went to Sacramento to have a talk with someone, and he was told not to worry. He said the decision had been made to have a large state telescope and he said: ďno matter what happens youíre going to get it.Ē So you see, that eased Shaneís mind and showed him how the politics was shaping up and the politics was that the state wanted to own a big telescope.

DeVorkin:

What about observatory politics? Was everyone fully in favor of the 120-inch?

Kron:

At that time, yes. But before that, oh this is something interesting, if you want to go back quite a few years?

DeVorkin:

Alright.

Kron:

I understand that when the Rockefeller money was made available to build the 200-inch telescope, it was first offered to W.W. Campbell, when Campbell was director of the Lick Observatory.

DeVorkin:

Wow! I didnít know that. Do you remember your source for that?

Kron:

No I donít. If I did I wouldnít tell you. (laughter) I think it was Mayall. I think so. It doesnít make any difference.

DeVorkin:

No, itís something that could only be solved now by going to the Rockefeller Archives or to Campbellís papers. Thatís interesting.

Kron:

It would certainly be there. I think itís true alright. And Campbell turned it down because he felt that it was too big a telescope; that they wanted the biggest telescope in the world. And Campbell felt that this was wrong. So they lost the money, this fortune, $7 million dollars or whatever it was. This would have been 1926 or Ď27.

DeVorkin:

When Hale was working very hard with the Rockefeller people?

Kron:

Well anyway later on it seemed to become apparent again, when Mr. Wright was in charge, that we could get a big telescope, and someone suggested a 60-inch and Wright wouldnít have it. The reason was that the tennis court was right in front of his house, the house that Katherine and I occupied after the war, and that was the only place on the mountain where it could go. And he didnít want to see the tennis court wiped out.

DeVorkin:

That is incredible. Totally incredible.

Kron:

Of course, thereís no tennis court there now, thereís a 120-inch telescope. But you see thatís what we were talking about.

DeVorkin:

Well Shane became assured at least that a telescope would be built, so the important thing from the direction of this interview would be what was your participation.

Kron:

Well in the design of the telescope we had to make several fundamental decisions. One was what the focal ratio would be. And the blank for the 120-inch flat was in Pasadena and was not used, it was never used for anything, it was never made into an optical flat. But it was brought to the first stages of being made into an optical flat. And we knew it was available and could be purchased very cheaply. It was in fact purchased for $50,000. So we had to decide whether we wanted an old fashioned F5 reflector which could be made out of that blank or one with a shorter focal ratio which meant we would have to get a new blank because the curve would be too steep for a blank prepared for a flat. So one time when I was home in Wisconsin, Shane wanted me to go down and talk to Otto Struve about this, and I did. I went down, this was in the winter, and I had a ghastly drive to Williams Bay from Milwaukee. I talked to Struve about it, to get his advice. And Struveís advice was for the F5 reflector, a standard old fashion reflector which is a good configuration, I think thereís no question about it. And at the time it was still a necessity because although probably the problems associated with getting good definition with a fast primary could have been solved later, it was a factor at the time. They hadnít been solved, except in the form of a Schmidt. And we didnít want a Schmidt obviously, we wanted a general purpose reflector. The Schmidt was the only form in which you could get good definition over a fairly large field with a fast primary. So we made that decision on the basis of support from Struve, that it would be an F5 120-inch reflector.

DeVorkin:

Why was Struve asked, do you believe?

Kron:

People down at Mt. Wilson were so full of F5 reflectors that we felt they would be biased in favor of an F5. We wanted an unbiased separate opinion by a person with a lot of experience.

DeVorkin:

What was McDonald?

Kron:

The McDonald is shorter than that. F4 I think.

DeVorkin:

Struve was around of course. He was involved in the building of that.

Kron:

Oh yes. He was instrumental in getting the money.

DeVorkin:

So it was an F5, and you could go with that.

Kron:

Then we bought the blank, the flat. We bought the 120-inch grinding machine — the design was just like the 200-inch. But the design was modified. The 200-inch design was a failure and so we abandoned part of the big grinding machine and turned it into an old fashioned type of machine thatís been used since optical parts began to be made at Lick. And it worked very well. It was a good job.

DeVorkin:

Did Shane start asking you to design auxiliary instrumentation?

Kron:

No. Of course I was supposed to design a photometer. And I did that I already had one that I used on the 120-inch. But Whitford took that over when he came and so my design for a photometer was never used.

DeVorkin:

That was already the late Ď50ís.

Kron:

Yes.

DeVorkin:

Well during the design stages of the 120, those working primarily were you and Mayall and Shane?

Kron:

Shane and Baustian, thatís right.

DeVorkin:

You also continued to work on binaries but you worked more and more in photometric work.

Kron:

Yes. Regular magnitudes. The think that got me into it was getting Eggen there. I met Eggen in 1948 at a meeting in Columbus, Ohio. Stebbins had three students, Huffer, myself and Eggen. And Eggen was on his way and we met him on the train going to Columbus. Katherine and I had been going east for some reason or other and we got on the train in Chicago and here was this great big guy in an Army trench coat, a big slob you know, and he introduced himself and I got to like him very much. And I recommended to Shane that we give him a job. We were looking for someone. All the astronomical society meetings then were practically nothing but meetings of people looking for jobs and getting slotted into jobs and things like that were going on. And so we hired Eggen. And he got interested in fundamental photometry, especially in main sequence stars. Through him I got interested in photometry of red dwarfs. BV photometry was PV photometry at the time, the UBV system hadnít been devised and PV didnít resolve the red dwarfs as a function of luminosity after a certain spectral type, you see. And I felt that if we went into the red spectrum region in which I was equipped to work that it would. And it did. I donít think Iíve ever gotten much credit for that by anyone except K. Strand, who looked at that and regarded that as something worthwhile at the time he was deciding who to plug in here[8] for director.

DeVorkin:

I see. Thatís what helped do it.

Kron:

Yes, he admired that very much. So I more or less drifted on, I got interested in fundamental photometry through that and drifted out of variable star work and I did photometry of red dwarfs in Australia in 1950.

DeVorkin:

Thatís the next thing we certainly want to come to. What was your contact in Australia?

Kron:

Father OíConnell.

DeVorkin:

Father OíConnell, from the Vatican?

Kron:

Well he was from the Vatican after that, but he was in Sydney at the time, and he was on the Board of Visitors, they called it, of what was then the Commonwealth Observatory. Prior to that it had been the Commonwealth Solar Observatory and they decided to change it to an astronomical observatory.

DeVorkin:

Thatís when they brought R.v.d.r. Woolley in, wasnít it?

Kron:

Yes, and Father OíConnell was looking around for talent like us to go down there and look at the equipment and see what could be done and we were questioned about equipment there. And thatís how Olin and I met Woolley. Woolley was director, you see, when we went there.

DeVorkin:

Eggen went down with you?

Kron:

Olin Eggen and I and Katherine, went together.

DeVorkin:

So that contact was double, that introduced both of you to the Southern Hemisphere.

Kron:

Thatís right and to Woolley, and M dwarfs. But Olin wasnít working with M dwarfs, he was working with early type stars. And of course this introduced me to the Small Magellanic Cloud through Gascoigne, S.C.B. Gascoigne. This last trip down there we worked on Magellanic Cloud clusters. I got something out of it too. Iím going to have to start writing pretty soon.

DeVorkin:

Based on data that you had taken in 1950?

Kron:

No, this time. In 1950 that was the Baade connection, you see. What we found was that the globular clusters in the Magellanic Clouds were too faint and this agreed with the factor of two distance, the intergalactic distance scale.[9] So Baade was enormously pleased by that.

DeVorkin:

Someone earlier had decided that there was nebulosity associated with these clusters and you decided to show that there wasnít.

Kron:

No. I didnít pay any attention to nebulae.

DeVorkin:

Who was it though that said these were generally uninteresting objects or something like that?

Kron:

Oh someone in the past, Iím quite sure. It may have been Solon Bailey. Olin Eggen dug that out, it was rather one of these interesting statements by someone who lacked imagination.

DeVorkin:

Well considering what Shapley was able to do with Baileyís work, you know that Bailey did not have the imagination. Was there anything happening at Lick that caused you to go down South?

Kron:

There was plenty happening at Lick that would have kept me from going down South. Stebbins was there, he needed help. But I managed to arrange for Stebbins to have assistance while I was gone and the equipment was working pretty well and continued to work while he was there.

DeVorkin:

Well, how did people like Shane take this?

Kron:

Oh Shane was enthusiastically in favor of it. He wanted staff members to be known for getting invitations like that. It added prestige to the observatory, I suppose. And after all it doesnít happen all the time and to have two of us go at Father OíConnellís request and Woolley wanted someone down there to look at their photoelectric equipment and make recommendations for it. And all of us wanted to travel to other countries. The work that I had been doing had demonstrated to me that the sample of red dwarfs available in the Northern Hemisphere was too small for what I wanted to do. I wanted to arrange them in sequence like Olin was doing, you see. So I was enthusiastic about completing the sample using the ones in the Southern Hemisphere. And there was a spirit of adventure involved. Of course it turned out that the work in the Small Cloud was the most important, that had some very important consequences. And one of them was to support factor of two, very brilliantly. Another one was that Gascoigne and I found the so-called blue cepheids in the Small Cloud. And that caused a real flap in the astronomical world and lead to an invitation for me to give a paper on this at the general assembly in Moscow at the 1958 IAU.

DeVorkin:

The reason why I brought that up in the first place was identify any question in your mind whether you were going to stay in Australia or whether you were going to go back, or what?

Kron:

Oh no, no question. Weíll go back for visits...

DeVorkin:

To Australia?

Kron:

Yes.

DeVorkin:

But at that time was there a possibility that you would stay in Australia?

Kron:

None whatsoever. I wouldnít have stayed. I didnít want to stay. For one thing it was very primitive place, the observatory was primitive, and Canberra was completely devoid of comforts. There was no good place to eat. The houses were terrible and it was a small struggling community that did not have the sympathy of anyone in Australia. Nobody wanted it except the people who conceived the notion of having a grand capital in Australia. And so the morale of the people in Canberra was low, the quality of the food was poor, both purchased food and prepared food. There was no entertainment worthy of the name. It was not an attractive place, but it was still an extremely interesting visit for a person who knew he wasnít going to stay and it greatly changed my world after that because I began to do very serious work on reddening because space reddening was the unknown factor in deciding on the relation between the intrinsic colors of cloud cepheids and galaxy cepheids, you see. So I went into six-color observing directed toward a multiple color approach to finding reddening but avoiding the blue and violet and ultraviolet spectral regions on account of metal absorption.

DeVorkin:

It gets very complicated in the blue.

Kron:

Yes.

DeVorkin:

What about Eggenís feelings about this? Because he, of course, eventually went down there to stay.

Kron:

Yes, he went down there as director, of course, when Bok retired.

DeVorkin:

Right, but he came back, when you came back?

Kron:

Yes he came back. I think he stayed a little longer because he was there during the fire.

DeVorkin:

Fire?

Kron:

There was a terrible fire not long after we left.

DeVorkin:

At the observatory?

Kron:

The observatory was engulfed. The observatory is in a forest of Monterey Pines, Pimur Radiata, that was all planted. An artificial forest for getting lumber. And during a dry spell, I think it was in January, Iím not sure of that, Olin wrote a paper for the PASP on the fire. That forest ignited upwind from the observatory and it swept right past, through and over the observatory. It wouldnít have been damaged except for the fact that sparks caught a pile of firewood that was piled against the side of the machine shop, and it burned up the machine shop. And it would have spread to the rest of the buildings except that they stopped it at an archway where the machine shop was connected only by a roof to the rest of the observatory building. Thatís where they stopped the fire. So they lost their machine shop and Olin came back not long after that, not because of the fire but because his work was finished.

DeVorkin:

During your time away, when you got back did you find that your ability to get things done at the observatory, were your various projects hampered by the fact that you were away at all.

Kron:

No, not at all.

DeVorkin:

So the atmosphere was still very very good?

Kron:

Oh yes, just fine. Those were the best years I think at Lick, about then when we began to have things.

DeVorkin:

Well during the Ď50ís Vasilevskis had come, he had been working primarily assisting Jeffers and other people like that. I guess it was Shane and Wirtamen who were working with the 20-inch Carnegie?

Kron:

They were taking the plates and counting the galaxies.

DeVorkin:

Right. Well during that time there was excitement over the Stebbins-Whitford effect.

Kron:

Yes, which was proved to be, unfortunately, not what they thought it was.

DeVorkin:

Is there any overlap between their discovery of the effect of the problems it caused and your interest in reddening?

Kron:

No. Stebbins had lost his interest in reddening and he was working mostly with six-color photometry of Cepheids to exploit the Wesselink method, or the Baade-Wesselink method I think Baade thought of it, but Wesselink worked it out and actually applied it and Baade never did.

DeVorkin:

I think that was characteristic of Baadeís research.

Kron:

And then also Stebbins was just doing six-color photometry of stars, just for posterity — bright stars.

DeVorkin:

So your work on the Small Magellanic Cloud was the element that was in support of Baadeís revision of the distance scale?

Kron:

Thatís right. Because the globular cluster magnitudes turned out to verify a factor of two.

DeVorkin:

But the Cepheids in the Small Magellanic Cloud are different than the ones here.

Kron:

Some of them are and some arenít. Later on Gascoigne did much more work on that. We still donít know a great deal about their colors. It turned out that there are Cepheids in the Small Cloud that have the same color/period relationships as Cepheids in the galaxy. But then there are some that are bluer. But there are in the galaxy too. The Population II Cepheids are bluer and it just could be that the Cepheids in the Small Cloud are just a mixture of Pop I and Pop II and that they donít separate physically the way they do in the galaxy and maybe they do, but for some reason or other interest in this died out and thereís been nothing more done on it.

DeVorkin:

Why do you think that is?

Kron:

I donít know.

DeVorkin:

Is there something that you sort of picked up on again?

Kron:

No, because what I did supported the reddening that Olin Eggen had largely determined which was about right. The result of all the six-color work that Svolopolous and I did[10] was to support qualitatively Olinís reddenings. S. Svolopolous and I got more accurate ones, thereís no doubt about it, but Olin had made only small systematic errors. And so it resulted that people had said that the galactic Cepheids were red because they were reddened more than we thought they were and that intrinsically they were the same as these blue ones in the clouds that Gascoigne and I had found. But it turned out that they were wrong, that Olinís reddenings were right and this meant that there was quite a large difference, about 2/10ths of a magnitude in B-V, between the two kinds of Cepheids. And then I donít know, after the Moscow meeting, it just sort of disappeared. There wasnít even any flap over who was right anymore. Maybe they just accepted that the difference was there, and nobody took an interest in going and taking the next step, finding out what it meant.

DeVorkin:

And nobodyís done that since?

Kron:

Not as far as I know. The last work that I know thatís been done on this was Gascoigneís extending the photometry. I was an undeserved co-author of that paper, it was in MONTHLY NOTICES. But Gascoigne thought I ought to be in on the last part of the work because I was in on the beginning, you see.

DeVorkin:

Letís talk about the instrumentation that you were involved in the Ď50ís. You attended, you were involved in the NSF Astronomical Photoelectric Conference and provided a paper on amplifying methods in astronomical photoelectric photometry and this was a meeting at Lowell Observatory in 1955. At that meeting people also were very interested and concerned in a site for a national observatory. What were the proceedings like?

Kron:

Johnny Irwin was present at that one. John Irwin was taking an aggressive interest in this. I think Meinel was there and I think Stebbins was, Whitford was, Bok was there. Stebbins loved to be in on meetings where great decisions were made. And he said it was essentially our group that decided to start the Kitt Peak National Observatory. That was Stebbinsí appraisal of the meeting after it was over and it was evident that the observatory was going to be funded.

DeVorkin:

Well the question of funding through NSF was one thing. There was a bigger question is to how it was going to be organized. What kind of cooperate body was going to administer it?

Kron:

I think that was done later. I donít think any decisions like that were made.

DeVorkin:

Did people talk about AUI at all at that time to your recollection?

Kron:

I donít even know what that is.

DeVorkin:

Associated Universities, Inc., the group that runs NRAO and there was a question at that time whether AUI was also going to run an optical observatory.

Kron:

I donít know about that. I had no awareness of that at all. It seemed to me that what was going on was a test to see if astronomers wanted an observatory that would be essentially Federally oriented.

DeVorkin:

Federally oriented?

Kron:

Federally funded and a national facility because we were warned that if the National Science Foundation undertook this it was going to greatly restrict the amount of money that astronomy at large was going to have. The money would go into Kitt Peak. And so at that meeting, they tried to get (they being whoever had a primary interest in starting the Kitt Peak Observatory) a feeling for how astronomers would react. Maybe ďtheyĒ were the National Science Foundation people.

DeVorkin:

They did not know it was Kitt Peak at that time?

Kron:

It wasnít called that.

DeVorkin:

Just the National Observatory.

Kron:

The idea was should the National Science Foundation go in for this major funding operation of a major facility. And they wanted to know whether astronomers felt that they could tolerate or get more out of this enormous amount of money going into one thing like that, or whether they would rather have the same money continue to be spread around all the relatively small observatories and university departments.

DeVorkin:

How did you feel about that?

Kron:

I donít remember having any feeling about it at all because I knew that no matter what happened I was associated with such a big well-heeled and well supported observatory that it really didnít make any difference to me. So I was in favor of the Federal idea — the money going to what turned out to be the Kitt Peak Observatory because I thought it would be a new thing for astronomy and of course the excuse for it was that it would give departments like the Yale Department legitimate and legal access to major observing equipment. And that is the way it turned out. I mean there have been flocks of people going down there from different departments doing big scale astronomy at Kitt Peak.

DeVorkin:

Indiana was very early in it, Michigan pretty much was the prime mover at that time. But your early contact with Struve, talking about a large telescope is interesting because he, in setting up McDonald of course, made it available to other subscribing departments of astronomy.

Kron:

They needed money. They rented it out you know. I think it was an economic necessity because I knew Elvey well. You see Elvey was in charge of a division at Inyokern and Elvey had been director at McDonald under Struve and hadnít gotten along very well with Struve either.

DeVorkin:

I didnít know that.

Kron:

And of course Franklin Roach was working with Elvey and I know Roach intimately. Iíve known him very well and weíre extremely close friends for years. And my impression from talking to them is that it was an economic necessity. They were just plain running out of money. In order to keep the observatory going they did that, because you canít partly close an observatory you know, you canít send the night assistant home and say: ďlook weíre only going to run for eight months this year, you go home and donít draw any salary for four months and then come back.Ē You donít do that.

DeVorkin:

Now this is getting up to a rather critical period in the mid to late Ď50ís. Iíd like to know how your interests were developing along these lines, the 120 was being built, were you active day by day in the design and construction of this instrument?

Kron:

No.

DeVorkin:

What were your major responsibilities?

Kron:

I didnít have any major responsibilities with respect to it, except to act as a part-time consultant and advisor on engineering aspects. So I had a lot of talks with Bill Baustian. In fact I went to Pasadena and back with him one time, the conversation was mostly about the 120-inch. And I was responsible for example for having an observerís cage at the prime focus instead of having a Newtonian configuration.

DeVorkin:

Someone was considering a Newtonian?

Kron:

It was supposed to be a Newtonian at the start, nothing else was considered. I thought that the advantages of having the observer at the prime focus would offset the disadvantages even in a telescope of that small size and so I pushed for this and Baustian and Shane and Mayall and I had a conference about this and decided to look into it seriously. We used Eggen for a model. (laughter) As a result of this, a mockup of a prime focus case, it really isnít a cage you know, it is a capsule, was built that would fit Olin. And it turned out to be optically practicable. The amount of light that was lost was only a little bit more than would be lost by a Newtonian design not counting the loss of the second reflection. With the second reflection with an old aluminum coat they were about the same. I think there was only about 7% more light lost as the result of what was occulted by the part of the cage that stuck out beyond what a secondary mirror would have intercepted. And of course the platform business was revolutionized, Newtonian platforms on big telescopes are real headaches you know. The one at the l00-inch is a deathtrap, itís a surprising thing that half a dozen people havenít been killed by that.

DeVorkin:

Has anyone been killed?

Kron:

No. No one ever has.

DeVorkin:

There have been some injuries though.

Kron:

Itís just surprising, no not at the Newtonian. Joy was rather badly injured down at all places at the Cassegrain focus. He fell off the Cassegrain platform. Thatís still quite a fall. Of course youíd be killed beyond a doubt if you fell off the Newtonian platform. So arguing for the cage was the sort of thing I did.

DeVorkin:

What about the fork design, I mean you had an F5. 5/l20-inch telescope. Who decided on the nature of the fork?

Kron:

Struve and I discussed that at Shaneís suggestion. Shane wanted to know what Struve would think about that.

DeVorkin:

Was Struve at Berkeley by that time?

Kron:

No. This was all at Williams Bay. And we were in favor of a fork for practical reasons because we thought it would be cheaper than the only alternative that was practical which would have been a mount like the 200-inch. We decided that was too big and bulky and expensive compared to the fork. I guess the way it turned out the fork is only barely practical. You see you get field rotation up near the pole because of flexure of the tymes of the fork.

DeVorkin:

Oh I see. When it was coming up towards the time for Shane to retire, what kind of talk was there around the observatory for his successor. What were the issues that the university was going for and that sort of thing.

Kron:

As I remember it there really wasnít much talk about it. There was a lot of speculation. Iím beginning to remember now what went on. There was talk about Mayall being the next director and Shane went around and polled the staff to see how everyone felt. I donít know how anyone else felt, but I felt that an outsider should be brought in in order to bring in new fresh ideas and Shane also got very close to individual staff members to try to find out a little bit more about them. I went on a trip with him to Southern California for example. And I went with him to a graduation at the Santa Barbara campus which of course put us very close together for days at a time. Finally Shane, who apparently had a lot to do with picking his successor asked for suggestions, and I suggested Whitford. As a result of this we were invited to the house of the person who at that time was president of the Regents, Don McLoughlin — you just saw him in the film.[11] McLoughlin talked to me about Whitford, wanted to know more about him. In any event Whitford got the job as you know. And Shane carried on as astronomer for a while and he wanted to see the job with the 20-inch through and finish the plates and the counting because that had to be done there because of the equipment necessary for counting the galaxies and the proximity to Wirtamen of course who was his ďco-counterĒ you might say. And thatís the way it happened as I remember it.

DeVorkin:

You never considered it for yourself?

Kron:

No, I thought it was too big a job. Iím no good at administrative work. Had Sproul stayed (I knew Sproul well and liked him very much) I might have given some consideration to the job but Sproul and Shane were going at once. Sproul had enormous sympathy for astronomers for some reason that we donít understand.

DeVorkin:

He was the assistant to Campbell when Campbell was president of the university.

Kron:

Maybe thatís what generated it because Campbell of course was an astronomer, it was possible that Sproul got that personal bias of Campbellís.

DeVorkin:

Thatís a possibility anyway.

Kron:

I donít know.

DeVorkin:

But the fact is you knew Sproul was retiring, did Whitford know that Sproul was retiring?

Kron:

Oh yes. Of course he did. This was common knowledge.

DeVorkin:

Well did you know what was on the horizon for the observatory?

Kron:

No, none of us knew what would happen and how great the reorganization of the university would be and how the observatory would fall in status compared with other departments and what would ultimately happen to the staff.

DeVorkin:

Well when did things start breaking?

Kron:

They started when Shane retired in 1958. Thatís when Stebbins of course left too. Not because of that but just that Stebbinsí sight was failing and he was getting very old.

DeVorkin:

Did he pass away in the 1960ís?

Kron:

He died after I came here to Flagstaff. So he died about 1966 or 67. It was one of those devastating years for astronomers, a whole lot of them died. Arthur Hogg died that year too and several others.

DeVorkin:

Well when did things start turning sour for Lick?

Kron:

You could see the handwriting on the wall about 1961 or 62. There was a good deal of talk among the other campuses about access to the 120-inch and there was a state of mind that felt that there was an old guard establishment on board at the Lick Observatory that was doing all it could to prevent people from other campuses from using the 120-inch for their own selfish reasons.

DeVorkin:

Who was generating this kind of thinking?

Kron:

Oh, I donít know really. I think it was a whole lot of people got together and decided on this.

DeVorkin:

Was it Berkeley primarily?

Kron:

No, I donít think it was. It wasnít UCLA primarily I know that. It could have come from San Diego, in fact I think some of it did.

DeVorkin:

That just leaves San Diego, there wasnít anything else really.

Kron:

There was some sentiment in Berkeley but it wasnít representative. Harold Weaver was one. And I think that if you want names, how intimate is this supposed to be?

DeVorkin:

You pass on how you want it used at the end.

Kron:

I see. Well the Burbidges of course, probably mostly Goeff I think but Iím not sure. And on our own staff I think that George Herbig was in favor of it.

DeVorkin:

In favor of what?

Kron:

Of opening up the observatory — of a complete reorganization with no central administration at Mt. Hamilton, and no central administration for the use of the telescope time, and I think that Whitford didnít really know what to do. I think Whitford was not a strong director. He didnít have his own ideas, he was trying to sample the way the wind was blowing and I think he wanted to jump, to use another terrible metaphor, on the band wagon and join the loudest and most powerful clique you see.

DeVorkin:

Where was Shane in all of this?

Kron:

Well Shane meticulously kept out of it. All he wanted to do was finish the plates with the 20-inch Carnegie astrograph and finish the counts. My impression was, Shane started that as a promise — he may have promised Wright heíd do it, or he felt that he had a responsibility to Wright to do it, to take the plates. But the counts were his own idea and I think that as they progressed he got extremely interested in this as a very worthwhile astronomical problem. And thereís still I think some possibility that those nebulae counts may be the most important thing thatís ever come from the 20-inch plates, but time will tell about that when Vasilevskisí work is done. It is no longer Vasilevskisí I guess, is it? Heís retired now.

DeVorkin:

Yes. Klemola is in charge.

Kron:

Yes. Weíll see how it will turn out. But so far the only thing of real importance thatís come from those plates Shane-Wirtamen nebula counts.

DeVorkin:

What about the future of the observatory? How did you feel? How did your research progress?

Kron:

Of course all of my plans for using the l20-inch had to be shelved and the work I was doing on the electronic camera had been brought to a halt at Lick in 1960, and I kept it going by appealing to Bart Bok at Mt. Stromlo in Australia who had a big machine shop by that time. And I went to Australia and Bart Bok catered to the continued development of the electronic camera.

DeVorkin:

Thatís when it came to be known as...

Kron:

As the Lick-Stromlo Camera. And after that I kept it going by doing the work myself. I made parts by hand and I managed, actually to get the only grant from the National Science Foundation thatís ever been given for electronic camera work, as far as I know. And it was indicated strictly that it would be the only grant, that I had to use it with the expectation of getting no more money. And I used it to get outside machine shop work.

DeVorkin:

This was around 1960?

Kron:

This is later than that. This was about Ď63, I hired machinists and machine shops in San Francisco with the NSF money to produce parts for the model of the camera that worked and was perfected here at the Naval Observatory later.

DeVorkin:

So that by the time I was there at least, in Ď65, all of your work on the camera was done on your own?

Kron:

In 1965, the last few years I had all done myself or by hiring with NSF money.

DeVorkin:

Letís go back a bit though and get at the origins of the electronic camera. When did you first conceive of the idea of using this new design?

Kron:

It wasnít my idea at all. It was, the design came from Lallemand.

DeVorkin:

I know that you modified Lallemandís.

Kron:

Thatís right. My idea was, the Lallemand design required replacement of photo-cathode for each set of plates, you see. And what I wanted to do was to make use of modern materials and equipment to build a camera in which the photo-cathode could be preserved indefinitely and the plates removed in spite of the sensitivity of photo-cathodes to chemical destruction. This was supported by many years, one year after another of grants from the Office of Naval Research. And with the grants from the Office of Naval Research which would seem ridiculously small now, we hired Eric Papiashvili and paid his salary from there. His first name is really I R A K L Y, I think or L I, Ivanovitch, heís a Georgian. Stalin was a Georgian of course. With Ericís help we went through a very quick series of experimental developments in which Eric and I tried to learn something about electron optics and high vacuum techniques and the construction of photo-cathodes. And we went through a series of about two or three experiments and then we tried to design something that we hoped might take a picture at the telescope and it was a complete failure. Then we tried still another design, and the carcass of this is still out at the Naval Observatory, in which we actually managed to get pictures on the telescope using the 20-inch. I wasnít allowed to use any of the other telescopes for this, only the 20-inch.

DeVorkin:

You were only allowed to use the Carnegie-20?

Kron:

Thatís right.

DeVorkin:

How did you feel about that? Did you ask them to justify this?

Kron:

I felt that after being a rather highly regarded senior member of the staff that Iíd been reduced to something just a little step above the janitor but I was so interested in the development that I didnít really mind.

DeVorkin:

What was the reason?

Kron:

I donít know what the reason was. There was plenty of telescope time and other instruments that could be used but the 20-inch was very suitable for it. It wasted the talents of the telescope because it was a large field telescope, but it had good guiding facilities and it was a good telescope for the purpose. But later on when I wanted to use the tube, when it got to the point where we wanted to get some results, I was still not allowed to use anything but the 20-inch. So I was never able to do any astronomy at Lick with it.

DeVorkin:

By that time Mayall had left, is that correct?

Kron:

Yes.

DeVorkin:

Was he being treated in the same way you were?

Kron:

I donít know. I never discussed it with him. I suspected he probably was.

DeVorkin:

What was it? A new director comes in and sort of wants to build up his own staff?

Kron:

Yes, I think that was partly it. It was partly because Whitford didnít know which way to turn I think. There were pressures put on him by the new president of the university, and pressures put on him from San Diego, and then there was the organization of a committee, of which I was a member, I didnít know it but it was really a burial service, because none of the evidence that was given was used by the committee at all.

DeVorkin:

What was this committee?

Kron:

It was named after somebody who was the dean of one of the schools at San Diego. Roger Revelle. If youíll pardon the term, I thought he was an ass. And it became clear after a while that the only reason for establishing the committee was that it was a sop to people who didnít like what was going on. Maybe Iím getting bitter now but to me it looked as if it had been a frame up to present the appearance of making an effort to analyze the situation. But at the time I felt, after several meetings of this committee, that the decision as to what would be done had already been made. And that the results of the committeeís deliberation were given no weight at all. And Revelle was clearly hostile, and Bob Brode was hostile. By hostile I mean that they were against preserving the Lick Observatory as a unit on its own. And they wanted and were successful in changing it into a facility for the university at large. And of course the Lick Observatory staff became the teaching staff at Santa Cruz, which is a very nice place to work.

DeVorkin:

Well yes, it certainly is. I understand that they had other options, they could have been split up and sent to all the other campuses.

Kron:

I donít remember. That wasnít discussed to my knowledge at the time. There seemed to be at the time a strong enthusiasm to build. There was a state of mind existing at the time in which the central administration in Berkeley, wanted each campus to be well known for some effort in some particular field. And so they decided that astronomy would be suitable for Santa Cruz. Therefore they wanted the best of the astronomical talents of the whole university to be centered in force at the Santa Cruz campus. So they now operate something that is called the Lick Observatory down there on the Santa Cruz campus and thatís the address of the Lick Observatory. Mt. Hamilton is just an observing station now. I think itís working alright. It seems to me from this point of view and after the lapse of this amount of time that itís turning out very well.

DeVorkin:

While all of this was going on, youíve already starting talking about how you were being treated, can you assess why you were being treated in this way. I think Iíve already asked you that question but Iím asking it again.

Kron:

Well I think probably I seemed like an old fogie at the time because Iíd been there for a long time.

DeVorkin:

But you were a contemporary of and you maintained friendly contact all your life.

Kron:

Thatís right. Of course Iíd done a lot of things that Whitford would have liked to have done. I think the thing that made the biggest change perhaps was the fact that I came out with a very (what I think) splendid paper, and I think a lot of other people agree with this, on the technique of using photomultipliers for astronomy in 1946.[12] That of course changed all of photoelectric photometry. That paper was so highly regarded that it wasnít published immediately, it was passed around the Yerkes and McDonald Observatories — the manuscript — before it went into the ASTROPHYSICAL JOURNAL.

DeVorkin:

I didnít realize that. Why did they do that?

Kron:

So everybody on their staff could see it first and get started. Someone told me that.

DeVorkin:

Well then Whitford was working on his own device at Washburn?

Kron:

Well he was working on the same thing, but you see I had had this little grant Stebbins gave me and simply assumed that that gave me the green light to go ahead with multiplier development. And I had a head start because I started making amplifiers at Inyokern after things slackened, but before the war was really ended, there wasnít enough to do. So I started working on amplifier development and I even had the machinists there turn out some parts for a photometer. So I had things on the 12-inch telescope within a few weeks after getting back at the end of the war. And in addition to this I had DC amplifiers that would run recorders instead of using a galvanometer. And I had a recorder that was supposed to be dumped into the sea from the Navy and these were passed out at Navy bases, just given away. So I got one and took it with me and I was able to do DC amplifier recordings right away when I got back. I was way ahead of everybody else and I even made predictions in that paper about pulse counting, which is the way a lot of it is done now, but it couldnít be done properly then because the pulse counters werenít available.

DeVorkin:

Do you feel it is possible that Whitford was somewhat envious of this?

Kron:

Itís more than possible. Stebbins was rather mortified by all this.

DeVorkin:

Why so?

Kron:

Well, we were both close to him you know and he didnít like to see anything happen that would cause friction. We were both civilized so we didnít really exhibit any friction. There was some feeling but weíve always been friends.

DeVorkin:

You still recommended him for the position at Lick.

Kron:

Well you see, this didnít show until later on really.

DeVorkin:

I see.

Kron:

I found out from Stebbins later how very deeply Whitford was affected. He was completely surprised by that publication in 1946. Had no idea I was doing anything on it at all. And instead of complaining to me he complained to Stebbins and asked Stebbins how he could possibly have allowed me to do this. Instead of letting Whitford do it you see.

DeVorkin:

Do you think he might have sent him a preprint too?

Kron:

There wasnít any preprints in those days.

DeVorkin:

So you just sent something direct to the journal.

Kron:

Thatís right. People didnít try things out as much on other astronomers then as they do now.

DeVorkin:

Thatís an interesting difference. When did you actually start working on the electronographic camera?

Kron:

1958. And it was started by Whitford. Whitford asked me to do experimental work on this. He wanted me to write a proposal for the Office of Naval Research because I had had several contracts before that and he knew that I was known there. I knew the people and could get contracts. So he suggested that I go into this, and I was interested in it. Iíd always wanted to do high vacuum work and photo-cell work. So it combined all the things that, from a point of view of laboratory technology, appealed to me. And in addition to this weíd just gotten a new laboratory at Lick and I had designed the laboratory building.

DeVorkin:

That was the new building?

Kron:

Yes — the laboratory facilities there, you see, and small local shop facilities, an electronics shop and things like that. This fitted right into these new facilities that were available. So I took to this eagerly, it really did interest me very much.

DeVorkin:

Did he have a time limit in his mind?

Kron:

He didnít say anything. He didnít say anything about a time limit, but it should have been obvious to anyone who was a technologist and Whitford was a very good one, that this was going to take a long time, many years. And of course before we had something that worked well, it took seven years. I thought it was rather quick. This was done in spite of the fact that support was withdrawn about 1959.

DeVorkin:

After just a year?

Kron:

Only just about a year, 1960, two years. The first year Eric and I went through all of our obvious mistakes that we knew weíd made and during the second year we got a tube that would take pictures. At the end of the second year we conceived a design that might work and that could reasonably take more than one picture at the telescope. And then when I went to Australia when Bart Bok supported the work, I combined my ideas and Papiashviliís, and completely changed the design of the tube to be that which was known as the Lick-Stromlo tube. It was built at Stromlo, the two of them were built there.

DeVorkin:

Was Bok aware of the fact that you had lost support at Lick?

Kron:

I told him. I appealed to him. I said: ďdo you want to help with thisĒ, and he said yes. And of course I did observing while we were there too as well as the electronic camera work. And he said yes, he would be enthusiastic about this.

DeVorkin:

Were you thinking of the possibility of staying down there when you went down?

Kron:

No, no I wasnít. Iím not sure I could have but itís possible that I could have. But we didnít want to move there at the time. Of course at that time the first glimmerings of what would happen to the Lick Observatory were noticeable. That was 1960 to 1961. There were only the murmurs of what was to come. So at the time I went to Australia I didnít realize that things would change so much that Iíd probably want to leave there.

DeVorkin:

So falling out of favor because of whatever reason and having more and more trouble working on the tube was not a deciding factor for leaving?

Kron:

No, it wasnít, because before I left we were taking first close pictures with the tube. We had been down to Mt. Wilson with it and had it on the Coude spectrograph on the 100-inch and got superb pictures.

DeVorkin:

And yet you couldnít get it on the l20?

Kron:

Oh no this wasnít allowed. This was not permitted. It was Herbig who pointed out that we had to use liquid air and liquid air would probably damage the mirror. And so we demonstrated that you could pour liquid air on large mirrors without damaging them and this had absolutely no effect, so that was just an excuse to keep it off the 120-inch, no question about that.

DeVorkin:

Was Herbig behind this with Whitford?

Kron:

Sure.

DeVorkin:

What reason would he have?

Kron:

Well you want to use the term jealousy? He was on the ascendency and I was on the way out. We were the people who were at the right age to wield clout there you see. So I feel it was a transparent case of one staff member doing all he could to destroy the career of another one.

DeVorkin:

What about Walker? When did he arrive? Of course he used the Lallemand tube. Who brought him?

Kron:

Merle, well I was instrumental in getting him the job at Lick. I know this sounds funny but I got Harold Johnson into the department at Berkeley. Harold Johnson came to Inyokern when I was there and, well weíve been pretty frank about this, I might as well continue. I never really liked him personally very much. No one else did either. He was beaten around from pillar to post, but I thought he had some genius.

DeVorkin:

He certainly understood magnitudes and color systems.

Kron:

Oh sure. And I felt that something should be done to get him, he had been at the University of Denver or someplace like that, a University that I never heard of before, with no astronomy department at all, and he had a burning interest in astronomy. So I thought he ought to be encouraged to get into professional astronomy and of course he had to go to a department with some reputation.

DeVorkin:

This is before he worked at Yerkes?

Kron:

Oh yes, this was where he had his Ph.D. He got his Ph.D. at Berkeley. I was on his committee.

DeVorkin:

When was this?

Kron:

Well it must have been about Ď48, very soon after the end of the war. I almost brought him with me.

DeVorkin:

Did Johnson learn his color systems then from you?

Kron:

He learned photometry from me and he was essentially my student. But not in an intimate sense. We didnít cooperate closely but I helped him with his thesis work and introduced him to the world of photoelectric work, but he was such a brilliant person that he had really no need for anything except a glimpse of what was going on in order to assemble all of the important features and go off on his own. He was soon off on his own and effectively too. It wasnít a random badly directed thing but he had good direction within himself. He knew what to do and how to do it and he did it. He did it well.

DeVorkin:

But he was a student basically and then he went on to Yerkes after that?

Kron:

He was never an employee at the University of California, he was only a student.

DeVorkin:

What about Walker, when did he come?

Kron:

I canít remember exactly but it was quite a long time ago. I think it was about the time Harold Johnson left.

DeVorkin:

Walker came as a faculty member?

Kron:

Oh yes. Walker joined the staff at the Lick Observatory.

DeVorkin:

And you were interested in him because he would develop and use the Lallemand system?

Kron:

Well I liked him personally, although heís another one of those people with a controversial record. You know he was hard to get along with and you have to endure a lot of things from Merle but itís pretty clear if you know him very well that this is tolerable, I mean heís just frank thatís all. Heís not brutal or anything like that. So Merle and I always got along well but we never worked together except with Lallemand tube. Merle took an interest in that. He had been in France you know, he speaks French fairly well. His wife is Hungarian. And he got to know Lallemand. I donít know if it was while he was in France that this happened or not, but there were a lot of things happening at once. When I was in Australia in 1950 I met Gerard de Vaucouleurs there. And Gerard knew Lallemand. We had a lot of discussions, Gerard and I got to know each other quite well in Australia. And I pointed out the need for infra-red sensitive multipliers. At the time we were there I had photo-cells for my red work.

DeVorkin:

The mosaics that you built up.

Kron:

Little tiny ones. And, ďOh,Ē he said, ďhave you ever heard of Professor Lallemand?Ē and no I hadnít heard. He said: ďheís got multipliers of this kind, why donít you correspond with him?Ē And so I did and I went to Paris finally to have a look at what Lallemand had. He said he wouldnít send his things. You had to carry them by hand. And when I got there he started to talk to me about electronic cameras but I had no interest in electronic cameras at all then. I was just interested in multipliers and I saw their production and how they did it. And I was impressed, it was obviously good.

DeVorkin:

This was right after you got back from Australia?

Kron:

Yes. About Ď51 or Ď52. I couldnít get infra-red multipliers from him right away. He had I think quite a long waiting list. But when some were available, Shapley carried one by hand from Paris to Berkeley in a little box.

DeVorkin:

How did he get involved in this?

Kron:

He knew Lallemand you see and Lallemand had told him who the multiplier was for and of course I knew Shapley and I think it was Allen Shapley who brought it to Cambridge and then Shapley himself brought it to Berkeley. So anyway thatís how I got my multipliers. And after a while Merle showed signs of becoming interested in the electronic camera. As I remember it, I acted as a go-between, between Lallemand and Merle. Iím not sure Merle knew Lallemand. But Iíve rather forgotten all this now. And I wanted to get Lallemand there because now of course since I was in the electronic camera game — I actually started work in 1958, but I began to be involved in 1957 writing the proposal and getting the contract for the Office of Naval Research. And I worked with it somewhat myself in 1957 before Eric came, Eric Papiashvili. So that nothing seemed to happen until 1958 but actually I put time in in 1957. So I of course wanted to see Lallemand there so I could study his methods. I had lost the opportunity to do it in Paris because I hadnít shown any interest. So Lallemand and Duchesne actually came to Lick, stayed several months and brought their equipment. When the equipment came all of the envelopes for the electronic camera had been destroyed in shipment.

DeVorkin:

The envelopes?

Kron:

They were glass with arms on them, they had a wing span of nearly three feet, all made out of glass. And Lallemand and Duchesne looked at the wreckage and decided it was hopeless. So the morale was at a low point and here both Duchesne and Lallemand had come all the way from Paris accompanied by three complete electronic cameras. It was clear that they wanted to turn this into a big thing, you know, this was their opportunity to get the camera started in the United States. And it was regarded as a great opportunity for the Lick Observatory to have this equipment. So when it was discovered that the envelopes were broken why there was a serious collapse in morale. The morale of course folded around Merle and Lallemand and Duchesne. Eric and I had been completely independent working on our own ideas and I actually avoided learning about the Lallemand tube so my thinking wouldnít be restricted by Lallemandís technique. I had only a general overall concept of how it worked. And I wanted to keep it that way. But by this time I was willing to learn a little bit more about it because we were trying to build a functional device.

So Eric and I got together, we knew the glass blower in the Physics department at Berkeley, who was very good. We looked at the wreckage one night after dinner and we decided that we could salvage enough glass and one body of the tube so that this remarkable man at Berkeley could probably repair it. And I talked to Lallemand about it the next day and well he said he didnít think this was possible but it was worth a trial. So I took the pieces down to this man at Berkeley and he made the repair. But there was a ground surface, a ground and polished surface that made the seal through which all of the parts were assembled and then sealed with the entrance window later on that was destroyed by the reconstruction and Lallemand said well it was still hopeless. So on another night Eric and I got together like the little pixies for the shoemaker or whoever they were, and we reconstituted the seal. And Lallemand said it was the best seal heíd ever had. Heís quite a gentleman you know, a remarkable man, completely unselfish.

DeVorkin:

What was he doing all this time while you were doing all this work?

Kron:

Oh they were amusing themselves somehow, it didnít take long. I took the tube parts down to Berkeley and waited while they were repaired and brought them back. And then when Lallemand looked them over and decided that it still wasnít any good that same night Eric and I got together and reworked that seal. We ground it, polished it and reformed it, and the next day they were ready to examine it and have a trial and it worked.

DeVorkin:

After that then Merle Walker took over?

Kron:

Merle took over the Lallemand tube, yes. Lallemand and Duchesne were there for quite a while. We took them down to our house in Carmel and they were guests there and immensely enjoyed the scenery down there you know and this used up some of the time. And Merle and Lallemand wrote a very good paper for the PASP you probably know about. I have referred to it — in fact they wrote two papers. Both of them very good. Well this, glimpse of the methods really didnít help me very much. It was a ghastly process. It was really terrible. It took a whole day to prepare the camera and then if you exceeded the point of no return and released the photo-cathode from its capsule you had only a matter of 6 or 7 hours in which it had to be used or abandoned. And it had to be abandoned if it was a cloudy night. You then had to do it all over again. Another whole day of preparation. Itís better now. It will last for about a week, so you can get through a cloudy week with it. Itís used all the time in France, very successfully and effectively. But itís still a tough road to hoe and has a very small photo-cathode. Lallemandís new tube has a ten centimeter photo-cathode but I donít know what the state of that is. Itís been used at Haute Provence I think, but just how actively itís used now I donít know. Anyway we went on with our own development.

DeVorkin:

You were trying to design some way to get around this necessity of destroying the envelope?

Kron:

Yes and the cathode, and having to take everything out and reprocess everything.

DeVorkin:

So obviously it was a valve, of some, sort?

Kron:

Yes. We were thinking both in terms of a valve and of a thin film barrier. And when Lallemand was our guest down in Carmel we had talked about this and Lallemand felt that the barrier wouldnít work. This is of course is what worked finally for the Spectracon and did not work for Al Hiltner. He was working along the same lines. So all of these methods ultimately worked and Lallemand didnít think a valve would work either but he felt that that was a better way to go. So thatís the way we went. Actually we didnít really give much consideration to a barrier type tube.

DeVorkin:

The Spectracon uses that now?

Kron:

Yes.

DeVorkin:

Who developed that?

Kron:

McGee in London, Jim McGee.

DeVorkin:

Well, getting back to your own development, what were the steps by which you began designing this valve?

Kron:

They started with existing technology. At that time there were some ball valves available. And Eric and I were thinking in terms of using teflon for the seal. Teflon seemed to have a very low vapor pressure, and we didnít know at the time that it reacted chemically with the alkaline metals which of course it does, it reacts violently with cesium. But nevertheless we actually built a tube that had a bronze ball with a hole through it that was driven by a lever from the outside that worked just like a valve. You turn it 90 degrees to shut it off and back 90 degrees to open it. And we managed to make it reasonably vacuum tight by having double seals everywhere. It was a labyrinth of drillings and little ports and everything, so that you could evacuate between seals. And this meant that the seal inside was well outgased and that you had two series of vacuua — a relatively low vacuum that backed up the critical seals and then the ultra high vacuum in the tube itself. But the seals were made out of low melting point materials like lead and indium. We were using indium metal for seals, and copying some of the Lallemand techniques for the big seal at the end for the window. We finally developed the Lallemand method to a point that Iím sure Lallemand would have loved, by having an optical flat for the window and a very carefully ground seat. And then having a heavy coating of evaporated lead on the window. And when the window flexed from the vacuum this made a line contact with the seat and the pressure was so high that the lead created a perfect high vacuum seal. It worked beautifully, but our old models couldnít be baked. Neither Eric nor I realized the vigorous baking that had to be done to make a photo-cathode exist indefinitely in a tube and not be destroyed by the chemistry of residual contamination, And so it wasnít until we got on to the techniques of gold seals that I learned at Princeton at the Plasma Physics laboratory there where the Stellerator was built. I managed to worm a invitation to come there to look at their methods for managing ultra high vacuums and I learned about gold seals. I brought this back to Lick, and then we learned about metal to sapphire sealing — that you can braze sapphire to metal. And thatís what we needed. That and the coin valve which was devised first at Stromlo. The coin valve and the method of operating it came from Stromlo — no seats, nothing that rubbed on anything. The coin rolled in and out. And then the method of sealing the tube came from sapphire to metal seals and Eric devised a method of disassembling the front after it was no longer possible to get the front of the tube off, this was all sapphire and welding you see. We split the tube, in the middle, this was Ericís idea, and assembled the electrodes in two halves so that the tube could be taken apart and cleaned and reprocessed. It was that concept that produced the tube that worked. And from then on it was just a matter of refining — finding out where the weaknesses were and ironing these out. So by the time I left Lick we had a nice working tube. But it was not appreciated at Lick by this time, it was regarded as a thorn in the side of everybody, that it was taking too much time away and that my salary wasnít being properly used. It was really very unpopular.

DeVorkin:

Did anybody come out directly to you and tell you this sort of thing?

Kron:

No, this was all done by innuendo.

DeVorkin:

Not one person on the staff?

Kron:

Nobody ever told me that it was time to quit and do something else.

DeVorkin:

What kind of relations did you have with say such people who seemed to be as fair as Vasilevskis?

Kron:

Oh Stan and I were always good friends.

DeVorkin:

But when it came down to the camera?

Kron:

He had nothing to do with this at all. It was a collusion between Whitford and Herbig. Herbig by that time was very influential at the observatory.

DeVorkin:

But Vasilevskis was certainly aware of these things?

Kron:

Stan really didnít know much about it, no. Stan was just occupied with the 20-inch program, nothing else. Anybody who was doing anything that had any promise of using the 120-inch telescope was very unpopular because this was supposed to be, reserved for the ďreally importantĒ people at the Lick Observatory, the ďgood astronomers.Ē

DeVorkin:

Youíre saying that with your tongue firmly planted in your cheek attitude?

Kron:

Yes.

DeVorkin:

There were also people like Kinman and Wampler around.

Kron:

Oh Kinman and I always got along fine. They werenít in this at all. I donít think they even knew what was going on. Although Wampler may have because he was very close to Herbig. But Wampler is an awfully nice fellow.

DeVorkin:

He was also very young there at that time.

Kron:

Yeah, he was very young.

DeVorkin:

Was Preston involved at all?

Kron:

No, George wouldnít ever have been drawn into anything like that.

DeVorkin:

The two major people that left, with the move immediately, were you and Preston. Kinman then left a little later.

Kron:

Yes. Kinman left and of course Mayall left, you know, he was the first one.

DeVorkin:

Oh Mayall left immediately?

Kron:

He was the first one.

DeVorkin:

Did you know why George Preston left?

Kron:

No.

DeVorkin:

Nor any of the others like Kinman?

Kron:

No. And Merle Walker wanted to leave, you know.

DeVorkin:

I didnít know he wanted to.

Kron:

Oh yes. And at the last moment he got cold feet, I offered him a job here. After I was here we had a vacancy and then he got cold feet and he didnít take it.

DeVorkin:

He went down to Cerro Tololo for a while.

Kron:

Yes, heís worked down there. He took one of the Spectracons down there and did work down there with the Spectracon. Spectracons are highly portable you know. Very easy to use. It has a lot of difficulties but ease of use and portability are not among them.

DeVorkin:

Were you involved at all, or interested at all in development of the Carnegie image tube?

Kron:

Not at all. My feeling is itís just a prop, itís a light amplifier and you lose almost as much as you gain. You gain a good deal of telescope time but you lose in signal noise ratio notice, if you read the publications on these things, that there is very little quoting done on the signal noise ratios with the Carnegie tube. Not that it isnít a useful thing at all, its obviously a useful contrivance.

DeVorkin:

For spectra?

Kron:

Itís great for spectra, yes. And this is partly because most spectra, before the use of the tube, had more information then was needed. They were widened too much and exposures were artificially long. And when the Carnegie tube came along they put no more information, this is just a by-product of the coarseness of the grain and properties of the fluorescent coating. They began to put no more information than was really needed in the spectra, and so they got spectra in much shorter time and it still had a satisfactory signal noise ratio. At least thatís roughly the way I analyze why the Carnegie tube worked so well. It does work. Itís a good tube. But the electronic camera is in a class by itself.

DeVorkin:

The spectracon is what kind of a design, is it more like a Carnegie tube actually?

Kron:

Oh no. Itís an electronic camera.

DeVorkin:

It is.

Kron:

Oh yes. Now the Lallemand method has the photographic plate in the vacuum along with the photo-cathode This was Lallemandís enormous contribution and it was done by cooling the plate with liquid air. You canít run a Lallemand-type of electronic camera without a liquid gas for a coolant. The big difference was that in the Spectracon a film of mica about three to five microns thick formed a barrier between the atmosphere and the ultra high vacuum and by putting 40 kilovolts accelerating potential you could drive the electrons through the mica and still have 20 to 25 kilovolts of residual energy left. Of course the electrons scattered terribly in the mica, very very badly, so this meant that in order to get acceptable definitions the film, the photographic emulsion, the silver halide emulsions made for nuclear track work, had to be pressed into intimate contact with this very very fragile piece of mica that was already under this stress of full atmospheric pressure. And any particles that scratch the mica would upset the crystal structure and weaken it and it would fail after that. So practically all the Spectracons failed in time and I guess they still do, and theyíre still being made I think. They do work and they do produce a lot of astronomy. They make very good pictures. And theyíre extremely easy to use; theyíre just as easy to use as the Carnegie tube, but theyíre much more easily destroyed. You have to have, a lighter touch to use them successfully. Merle used them a lot. He got to know McGee very well, and was able to get a supply of them right out of McGeeís laboratory.

DeVorkin:

Okay, letís talk about your leaving Lick. Youíd been there for so many years, was this sort of a family decision?

Kron:

I think it was probably my decision, wasnít it, leaving Lick.

Mrs. Kron:

I guess so.

Kron:

I guess it had to be.

DeVorkin:

What was the situation? Did you have a job before you left or what?

Kron:

Oh yes. Well I looked for a position and I had five offers, was it? I think it was five offers. One of them was in Rochester...

Mrs. Kron:

The Optical Institute.

Kron:

There was one at Meinelís Optical Institute (The Optical Science Center) and there were two others, I canít even remember, I guess I could have given them absolutely no consideration at all.

DeVorkin:

Was there a possibility of going to Australia?

Kron:

No I didnít look into that. There might have been a possibility of going but I didnít try to exploit it.

DeVorkin:

You mentioned that Bok told you later on that he would have been interested in you as his successor down there.

Kron:

Yes he was.

DeVorkin:

But you didnít pursue anything at that time?

Kron:

No, I didnít want to. I had accepted a job here.

DeVorkin:

Already.

Kron:

Yes, already. Thatís the timing isnít it. It was in Hamburg that Bok talked to me.

Mrs. Kron:

Yes, we were already here two years.

Kron:

We were already here, thatís right. I just felt it was an attractive thing but I just couldnít leave after taking this job. It wouldnít have been fair to Kaj Strand or the Observatory. And it was a very nice job. I could see that after I got here that it was just as if it had been made for me because there were very little administrative responsibilities, practically all of the administration that was onerous took place in Washington. And they brought me here to continue with the electronic camera. I was offered time on the 6l-inch. I had a lot of time on the 40-inch, all I wanted, after all I was in charge. And I could commandeer all the time I wanted on the 40-inch, which was very well adapted for electronic camera work. We had a machine shop that I was in charge of. And I was given all the money I needed. We bought a liquid air machine, we equipped the place with the finest ultra high vacuum equipment, and just simply went ahead without any restrictions or anything. It was like a kid in a candy store, with the proprietor in the back room practically, so I couldnít have borne to leave it. Every thing was perfect and I immediately designed and built photoelectric photometers for the telescopes. And this all went very rapidly and very successfully and I got the interest of several of the staff members in the kind of work I enjoyed. We soon overcame several of the residual difficulties with the electronic camera and corrected them. And this is still going on. Harold Ables has done a beautiful job of carrying that on, so that they have cameras now that you can carry around and put on other telescopes. Heís had it down to Kitt Peak. Heís gotten to magnitude 24.9 with exposures made with the Mayall telescope.

DeVorkin:

24.9!

Kron:

24.9, yes.

DeVorkin:

Thatís about what they think the LST is going to be able to do.

Kron:

Yes. But heís already done it with the electronic camera with one exposure, a long exposure, I think it was two hour exposure, but he still did it.

DeVorkin:

That says something for the dark sky brightness doesnít it.

Kron:

Yes it does.

DeVorkin:

Certainly at the Naval Observatory here though the astrometric reflector had an on-going program, were you administering that at all?

Kron:

No. I didnít want to administer it. And I did not take the time that was offered on the telescope either. After I got here I realized that all of the work I could do could be done very well with the 40-inch. And I didnít think that the program with the 61-inch should be meddled with at all. The telescope was built for a specific purpose, it was an excellent telescope for that and it seemed to me that the best way to use it was to let it be used for the parallax program, almost 100 percent. We used it occasionally for other things, for guests, but a good 90 percent or 95 percent of the telescope time continued to be used for the parallax program. I think Kaj Strand was grateful for that too.

DeVorkin:

That of course was his program.

Kron:

That was his program. Yes. He got the money for the telescope and engineered the design of the telescope. Itís probably the best astrographic telescope in the world.

DeVorkin:

Well, a lot of people are coming around to the use of reflectors now for astrometric work.

Kron:

Yes, astrometric. I should have said astrometric telescope.

DeVorkin:

For a long time these large reflectors were considered taboo.

Kron:

Well not with a flat secondary. I still donít know how good they are unless the secondary is flat. And I think this is still the only one with a flat secondary. But you see the secondary orientation is not important when the secondary is flat. You canít get higher order field corrections into the field by motion of the secondary. So it has some bad features, but they canít be helped — they come from the fact that it does have a flat secondary. The flat secondary is responsible for the success of the astrometric application. Itís an F10. Yeah the ratio of the focal length to the diameter of the mirror is ten to one, but it is effectively something like an F14 I think as far as light gathering power because of the size of the secondary.

DeVorkin:

How did they get around flexure problems with that.

Kron:

You donít have to, you see, it doesnít make any difference with a flat secondary.

DeVorkin:

You mean differential flexure?

Kron:

All it does is move the image. It doesnít put any field corrections into the field. At least nothing appreciable, the amount of flexure that is there. Itís not a particularly sturdy telescope, its not designed for super low flexure because it doesnít have to be.

DeVorkin:

In comparison lets say to the 120-inch?

Kron:

Itís more rigid than the l20-inch. And they already knew about the fork flexure in the l20-inch so the 61-inch was built with an extremely robust fork, a very stiff stubby fork. So there were no fork flexure problems with the 61-inch. At least nothing that was serious.

DeVorkin:

During your tenure as director here of the station did you become involved in Naval Observatory politics, association with the Navy and that sort of thing?

Kron:

No, none at all. No, I kept out of that meticulously. And when the directorship of the Division (it was called the Astrometric and Astrophysics Division) became vacant after Victor Blanco left I was invited to take it. And I decided that I didnít want to get into that. So I stayed here. And I was nicely rewarded for it too because I think that Strand realized I probably wouldnít have been any good at the job. Iím not firm enough to deal with the Civil Service state of mind. When people have been in Civil Service a long time their main idea seems to be to compete with each other for promotions, instead of to do the things they were hired to do. And there was none of that out here at all. I had seen that at Inyokern when I was a Civil Service employee there.

DeVorkin:

It looks like you even saw it at Lick.

Kron:

And there was some of it at Lick at that time, thatís right.

DeVorkin:

But not here?

Kron:

There wasnít a trace of it here and there still isnít. And so I decided I wanted to stay here in this atmosphere. And things were going well here, everybody liked me, and were cooperating. I had a chance to do my own work, you know, and get support from the staff. Nobody seemed to mind that I took quite a bit of telescope time.

DeVorkin:

You mean you would have had to move to Washington if you took Blancoís job?

Kron:

Oh yes we would have had to move our whole family to Washington.

DeVorkin:

Who was the director here at the station before you were here?

Kron:

Art Hoag.

DeVorkin:

And he went to Kitt Peak after that.

Kron:

He went to Kitt Peak before I came here. There was only an acting director here.

DeVorkin:

Then he was here before you and he might have set the tone of the place?

Kron:

Oh he did. He set the tone of the place. He hired the people and his charming personality showed through everywhere I think. And his skill was in choosing friendly people and people who were oriented toward a job instead of toward themselves, a very unselfish staff.

DeVorkin:

And it was maintained that way during your directorship?

Kron:

Well, yes, you see I of course reaped the profits of the care with which Art assembled his staff. I was very careful not to damage anything there. And Art of course had been interested in electronic cameras too. I think he probably recommended me for the job and thatís why I was brought here actually to continue electronic camera work.

DeVorkin:

So he was already well known to the community when he came back here to Lowell?

Kron:

Oh yes, I should say. Heís an outgoing person who does things for the community. Iím afraid Iím not. So he was well known and well liked with the towns people.

DeVorkin:

Why do you say that about yourself?

Kron:

Why I donít take interest in public functions. Iím just interested in astronomy.

DeVorkin:

So he was really outgoing?

Kron:

Yes, heís a very outgoing person.

DeVorkin:

He lasted a good while at Kitt Peak and then I guess he left under some kind of a cloud there.

Kron:

There was no cloud around him.

DeVorkin:

Around the mountain?

Kron:

Yes, thatís right. I know nothing about it except rumor, not having been there.

DeVorkin:

There are some general questions Iíd like to ask you. I donít want to keep you too long, itís 11:00 at night now. Youíve certainly seen astronomy change quite a bit.

Kron:

Yes, very much.

DeVorkin:

Especially at Lick. We didnít talk too much about J.H. Moore and W.H. Wright, did you have any contact with them other than what weíve mentioned. I mean what kind of personalities did they have?

Kron:

Of course Iíve had intimate contact with them. Moore taught me how to use the 36-inch refractor. That is to say I worked as his assistant in order to learn the game with the telescope. I had never operated a telescope that size, before, in my life you see, and had been responsible for it. At Lick you were the only observer, and you were responsible for the telescope, so you had to know how to use it and what the precautions were, where the dangers lay and things like that. So I worked for many nights just guiding the spectrograph with Moore. One of the things we did was spectroscopy of Saturnís rings when they were nearly on edge. I saw Saturn one night when they were on edge, you couldnít see the rings at all. I never worked with Wright, but I had a lot to do with him. He hired me, he offered me the job there and he liked me very much, and I liked him very much. But he wasnít generally liked by the young people.

DeVorkin:

Why was that?

Kron:

I donít know, I really donít. They regarded him as a old fogie I think, lacking in imagination, which I think was wrong because he was the one who engineered getting the Crossley telescope mirror aluminized. It was the first fully aluminized astronomical telescope which was used for astronomical research of any size. It had an aluminum coating on the mirror. When Wright heard about the process down at Cal Tech he aggressively went down there and asked them if they would be interested in considering the Crossley to be an intermediate size telescope that theyíd like to coat. And they did, they were interested in that. So they built a 36-inch tank in Pasadena in order to try it out on the Crossley before the 60-inch and 100-inch mirrors were coated, you see. And Wright did that, because he was interested in ultraviolet spectroscopy which he was doing with the Crossley after the aluminized coating had been put on. I thought he didnít deserve the reputation he had among the young people, which is being a formidable ogre type of person.

DeVorkin:

Did they ever talk about Campbellís term there.

Kron:

There was very little said. Campbell was not particularly liked. He was a slave driver apparently, and a meticulous old maid; sort of a person who had all kinds of rules that governed everything including the private lives of the people, whether you could own a dog or not, and how much bath water you could draw during the dry season, all kinds of things like that. Whereas the administrations after that saw to it that there was another pump put in and another spring tapped or something like that if there wasnít enough water to bathe with during the dry season. But Campbell wouldnít do that. He just wanted everything to stay the same and the people to live within the structure that existed at the time you see. So he wasnít well liked. Wright and Moore didnít like him.

DeVorkin:

What about Aitken?

Kron:

I had very little to do with Aitken. I never had any heart to heart talk with him. I met him when I was a student of Stebbins in Madison when Aitken gave a public lecture at the University. And then I saw him at Mt. Hamilton when I came out with Stebbins in 1935. We went up to exhibit me to the people at Berkeley and I met Aitken there, he was just about to leave. And I also met Campbell there.

DeVorkin:

You mean at Lick?

Kron:

Yes.

DeVorkin:

Campbell must have been almost blind by that time.

Kron:

Yes, he was almost blind. He committed suicide not long after that. He was up there for a visit and I met him up there.

DeVorkin:

After his National Academy years as president, did he go back up to Lick to live there or did he stay in San Francisco?

Kron:

I think he stayed in San Francisco. Iím not even familiar with the dates there. He was not living there when I was there in 1936, when I came. Neither Campbell or Aitken were there in residence.

DeVorkin:

I know that you were in residence when Campbell did commit suicide, and Iím pretty sure that was in San Francisco.

Kron:

Yes, that was in San Francisco.

DeVorkin:

What was the talk on the mountain?

Kron:

Well there wasnít any talk really, there was a shock. People who knew him well you know, the Moores and the Wrights, and Leslie Potwin, the long time secretary.

DeVorkin:

Campbellís secretary?

Kron:

Well, she was Campbellís secretary when Campbell was there, secretary when Wright was there, secretary when Moore was there, and then she retired about the time Moore did.

DeVorkin:

What was her reaction, did you see her?

Kron:

Well they were all appalled of course that this could have happened at all.

DeVorkin:

It was a complete surprise?

Kron:

Complete surprise. There vas shock but no sadness, nobody seemed really sorry.

DeVorkin:

How did he commit suicide?

Kron:

I think he jumped out of a window. Thatís all I know. There was very little about it in the papers too, in spite of the fact that he had been regarded as a prominent citizen, it was not very much covered by the newspapers.

DeVorkin:

It might have been a very embarrassing thing?

Kron:

Yes, guess it was. Nasty thing anyway, you know, for someone to do that.

DeVorkin:

But no one particularly talked about why he did it, or people didnít sit around trying to rationalize it?

Kron:

I donít remember any discussion about it at all. It was just pointed out that he couldnít bear the thought of being blind and decided it was just better to die. And I think that probably exactly why he did it.

DeVorkin:

Well on a happier note, you mentioned a few contacts with Henry Russell, maybe weíll finish up with that okay?

Kron:

Oh yes. Shall I tell the story about the darkening at the limb?

DeVorkin:

Absolutely, right.

Kron:

Well, of course in my thesis there was the matter of determining limb darkening in eclipsing binaries by making photoelectric observations, under the fine conditions at Lick, that were accurate enough so that the shape of the light curve in a eclipsing binary could be used for more subtle purposes than just getting orbital elements. And this interested Henry Norris Russell, and had for a long time, very much. And in 1938 when I got my degree, Horace Babcock and Dan Popper and I, who all got our degrees that year, were sent on a triumphant tour to the Eastern part of the country by Mr. Wright. We presented our thesis papers; two of us gave them at the American Philosophical Society and one of us, namely myself, gave it at the National Academy in Washington. And while we were in Philadelphia at the American Philosophical Society Meeting, Henry Norris Russell was there and he heard that I was working on this problem, but didnít know how far I had gotten. By that time I had determined the limb darkening of an eclipsing binary. And so he got me aside and invited me to lunch and said he wanted to talk to me about this problem. And finally it developed that he wanted to caution me not to try this. He was so certain from his own experience that it was impossible, that he thought I would be wasting my time, especially as a thesis problem. I had the fun of telling him that it had already been done. That it worked.

DeVorkin:

And his reaction?

Kron:

Well his reaction was very favorable. He was immensely pleased, and asked me, pried me for details and the value of the limb darkening co-efficients and things like that, and about details of how it had been done and how it had turned out. And then later on one of the things I found among the old guard at the Lick Observatory, is that Henry Norris Russell was not welcomed there. Mr. Wright did not like him at all, for reasons I donít know. Some people probably know but I never knew, I never tried to find out. And since he was such a charming person why I arranged with Donald Shane immediately after the war to get Henry Norris Russell there as a summer visitor, a research associate for the summer. Just so he could come and Katherine and I could talk to him and other people of course could talk to him. So we had the pleasure of his company for several months during the summer there.

DeVorkin:

His wife broke her arm during that time, or her foot?

Kron:

I think she did. She did slip and break, I think, her arm. The Russells used to go up to the Parapet every night and watch the sunset.

DeVorkin:

Did they? Thatís great. Did he used to talk or were you there when he did that sort of thing?

Kron:

Oh yes. We always used to stroll up after eating our dinner at the so-called boardinghouse at the time.

DeVorkin:

Do you recollect any of the experiences? I mean he was pretty much, a non stop talker wasnít he?

Kron:

Oh yes he talked a lot always about astronomy, and Mrs. Russell would always tell funny stories. Theyíre pretty well summarized in Katherineís publication that she wrote about Russell.

DeVorkin:

Could we ask your wife to come in.

Kron:

Yes.

DeVorkin:

Weíre talking about the experiences just post-war when the Russells were on the mountain. Both of you had contact with them. Did you know Russell before that? When did he give you these notes on binaries?

Mrs. Kron:

At that time. I had met him at Vassar first and then Iíd seen him at Harvard. He used to come up and talk to the hollow square meetings, every other Friday or something. In fact in the beginning I thought he was on the Harvard staff.

DeVorkin:

He was there that frequently?

Mrs. Kron:

Yes. Or at least I thought he was attached to it. And then Iíd also heard quite a bit about him from Frank Edmondson, who was there in the summer before I went to Harvard when I was a summer student. So I knew that the Russells spent their summers at Jamestown. And Margaret Edmondson and the grandchildren were there while Frank was at the Harvard summer school.

DeVorkin:

Jamestown, Rhode Island?

Mrs. Kron:

Rhode Island.

DeVorkin:

Right. Frank Edmundson was at Harvard in the mid Ď30ís, after they were at Flagstaff?

Mrs. Kron:

Well this was 1940 and then I spent the winter there, the next winter I was at Harvard.

DeVorkin:

What was it like having the Russells around for that summer?

Mrs. Kron:

It was really enjoyable. He was known as an eccentric, you know. They always looked at the sunset, did you mention that already?

DeVorkin:

Thatís why I figured it would be time to bring you in.

Mrs. Kron:

And then I understood that they also looked at sunrises, I think perhaps Mrs. Russell mentioned that. But we really enjoyed having them. He loved to lecture, I mean, they would have to gather up an audience Iím sure to feed it to him because he more than volunteered to talk.

DeVorkin:

Would he need an audience or just one other person?

Mrs. Kron:

Well he was there and I think that they felt they should use his talents as a lecturer. He used to lecture in the school house, remember, for some reason or other? Iím not quite sure why.

DeVorkin:

Thatís interesting. That was the one room schoolhouse by the fire station on the flat?

Mrs. Kron:

Yes.

DeVorkin:

Okay, I have a question for both of you to finish, up this tape. How did you agree on research projects?

Kron:

Ií donít remember any process, do you? To reach, agreement? Mrs. Kron; Well you had some and I had some. Iíd been doing spectroscopic binaries, so then I moved over to photometry cause, it took two people.

DeVorkin:

Youíd been doing spectroscopic binaries at Lick?

Mrs. Kron:

Yes.

DeVorkin:

Before Lick you were at Harvard.

Mrs. Kron:

At Harvard. I had to work on Bokís awful project, the neodymium radial velocities. And then they went and lost my answers too. The radial velocities from those lines in the spectra of stars. And I had to pay for doing that research as a student to get the credit for it, like Virginia at USC, paying for orchestra but not getting any experience.

DeVorkin:

That was the situation at Harvard for all Harvard students or people coming from Radcliff?

Mrs. Kron:

Well the Radcliff people had to pay $50.00 more than Harvard, as I found out later. And then some people were hired to do the same work that we were paying them to do!

DeVorkin:

And how did you feel about that?

Mrs. Kron:

I was kind of annoyed to find out that women had to pay more than the men, naturally.

DeVorkin:

That does sound a bit strange. You worked for Bok primarily, is that true?

Mrs. Kron:

Yes, he was my advisor. He was the only person at Harvard who paid the slightest attention to me.

DeVorkin:

Why was that?

Mrs. Kron:

Because I paid my tuition, I was not on a fellowship. I didnít know enough that you were supposed to ask for fellowships. My family were not academics, so they thought you had to need the money to get scholarships in the same category.

DeVorkin:

Did you get interested in astronomy while you were at Vassar?

Mrs. Kron:

Oh long before that. The American Museum of Natural History in New York had a junior astronomy club.

DeVorkin:

Philip Fox ran that?

Mrs. Kron:

Before him, never met him. This was 1930.

DeVorkin:

Before the planetarium?

Mrs. Kron:

Yes long before that. Iíd left New York before the planetarium. And then the eighth grade at the Brearley School had one term on astronomy. The Brearley in New York, the private school. And that was the same year I think.

DeVorkin:

And this is where you got interested. So we canít blame it on your husband.

Mrs. Kron:

Oh no, it was a long time before that. I was determined to major in astronomy when I went to college, and picked Vassar because they had a telescope.

DeVorkin:

Thatís right. Who was there at that time? Was Maud Makernson there?

Mrs. Kron:

Yes. And Katherine Stillman was there the first year.

DeVorkin:

But Maud Makernson was the one that was your primary teacher?

Mrs. Kron:

All the way through.

DeVorkin:

Her forte was celestial mechanics was it not?

Mrs. Kron:

Yes, but she didnít push it on us, it was beyond us I think.

DeVorkin:

What did she emphasize?

Mrs. Kron:

She got Dr. Trumpler to come for one semester. He lectured and we helped him with some of his computing and his velocity ellipsoids, just general work.

DeVorkin:

I guess he was working on that at that time.

Mrs. Kron:

We did F-stars for him or something. Just general astronomy.

DeVorkin:

It was understood that if you go on to graduate work that Harvard was going to be the choice or did you consider some other place?

Mrs. Kron:

Oh no, I donít know why I took Harvard. I went to summer school I guess, and it was easy to go back. And that was really funny when I showed up they didnít have the faintest idea who I was, and they didnít ask for an application. I just sent in my name. They thought I might be a little old lady amateur astronomer.

DeVorkin:

Did you have an interview with Shapley or something like that?

Mrs. Kron:

No, it was a summer course, they didnít care who came.

DeVorkin:

But then you went back, in the Fall. Did they interview you at that time, or ask you what you wanted to do in astronomy?

Mrs. Kron:

I donít remember. They just take anybody.

Kron:

That had the money.

Mrs. Kron:

I remember that Cecelia, Payne-Gaposchkin was particularly nice to me. She didnít have much status as far as running the place. I was scared of Shapley, at first.

DeVorkin:

But Bok was the most accessible?

Mrs. Kron:

I guess so. I was really out of my depth by then. Menzel was very nice too actually.

Kron:

They were all nice, Shapley was too, he was an awfully nice man.

Mrs. Kron:

It was. I shouldnít have been scared of him, but I was.

Kron:

Thatís right.

Mrs. Kron:

But I was really appalled at the salaries that they had. They were awful. I didnít see how they could eat. 50 cent lunches, 50 cent dinners. Virginia McKibben said you could have a car or apartment but not both. And somebody told me that they had just so much money and they had to make it go around. They had so many people they felt they had to support.

DeVorkin:

Were these salaries for women or were they for everyone.

Mrs. Kron:

Everybody. It was only Menzel that had a good salary. I think. Everybody else was on really a shoe string.

DeVorkin:

Why was Menzel singled out?

Mrs. Kron:

He was a professor at Harvard and I donít think anybody else had that title.

DeVorkin:

Oh I see. He was the only one and Bok wasnít?

Mrs. Kron:

Bok might have. That might have been alright. But there was Kopal and Prager was there, wasnít he?

Kron:

In 1940.

Mrs. Kron:

Heíd just been there. And they supported Pannekoek — they were hoping to get him out of Holland.

DeVorkin:

Shapley was doing this, trying to get Pannekoek out of Holland?

Mrs. Kron:

For some reason or other he kept talking about Pannekoek. Had he been in South Africa? I donít know because I never knew him at all.

DeVorkin:

This is a good lead because we can go back and check on the observatory records and of course they would have them there if that were true.

Mrs. Kron:

But they had an awful lot of people to support. There was Constance Boyd and Dorrit Hoffleit was there, Martin Schwarzchild, too.

Kron:

Thatís right.

DeVorkin:

There was a Chinese fellow there who since became the director of Purple Mountain.

Kron:

Oh, Yu.

Kron:

Yes.

Mrs. Kron:

But he wasnít at Harvard. I thought he was West Coast.

DeVorkin:

He might have been Yerkes. Okay we can check.

Mrs. Kron:

Becky Jones was there.

DeVorkin:

What was her position, by the way? Sheís written quite a few books in History and that sort of thing. But her training was in astronomy?

Mrs. Kron:

I think so. Sheíd just been at Lick.

Kron:

Yes.

Mrs. Kron:

And I asked her why she left because she loved it at Lick.

Kron:

It was Campbell meddling in private lives.

Mrs. Kron:

She said Mrs. Aitken was the one. Mrs. Aitken kind of wanted to figure out who went out with who. Campbell had gone by then, or at least the last six years.

Kron:

Iíd forgotten the Aitken administration. As a matter of fact Menzel was there at that time, wasnít he?

DeVorkin:

At Lick, yes.

Kron:

About 1931 or something like that, just before Nick and Art Wyse.

Mrs. Kron:

Goldberg was at Harvard too they were supporting him. He didnít have a job.

Kron:

He was there, thatís right.

DeVorkin:

All these people at Harvard at once, it must have been huge.

Kron:

Yes.

Mrs. Kron:

The place was crawling with them.

Kron:

Talent.

DeVorkin:

I know that Campbell did have a very conservative policy about women in astronomy, either women could be in astronomy as long as they werenít married or married they couldnít be astronomers.

Kron:

And they werenít allowed to use equipment either.

Mrs. Kron:

Well Mt. Wilson was the same way. There was really no future for women with Ph.D.s in astronomy unless you wanted to teach at a womenís college. And that didnít interest me.

DeVorkin:

That was the same thing at Harvard.

Mrs. Kron:

They wouldnít let me observe at Agassiz Station.

DeVorkin:

They wouldnít let you observe?

Mrs. Kron:

No, because there was no place to stay overnight if it was cloudy. That was what really bothered me. After I decided to go to Harvard and then they tell me this. Thatís why I really liked Lick, because I had a chance to observe there.

DeVorkin:

Well thank you very much. I just have a few more moments, on this tape but Iím getting pretty down to the end and itís 11:25.

Kron:

Itís been a long haul hasnít it?

DeVorkin:

As you look back over your mutual careers what do you feel has been the most significant part of your life in astronomy?

Kron:

I donít know. I donít think you could tell.

Mrs. Kron:

V444 Cygni was really exciting, because it was simple enough in those days and nobody had devised the hard way to do it.

Kron:

One of the first abnormal binaries in which the abnormality was coupled with something that you knew ahead of time. You knew that this was a strange object being a Wolf-Rayet star. And so you had the feeling that a detailed study of the light curve could contribute something to the understanding of these bizarre stars and I guess it did too.

Mrs. Kron:

And I was very pleased to find that the darn thing does vary from night to night because I just swore it did. You see I did the meter reading, and it should have been better than the answers that we got that were all over the place. And well, the mass transfer ideas hadnít been developed yet, you know, the sudden jumps of light.

DeVorkin:

But you had started on the clouds, the various shells for the suggested structure of Wolf-Rayets. And I know that was still very strong while I was a student in the 60ís and pretty much is the model today. That was the first suggestion of that model.

Kron:

Yes.

DeVorkin:

My beeper is telling me to end, so thank you very much both of you. You look very tired.

Kron:

So do you. (laughter)

[1]Pabst family Ė well-known manufacturers of beer.

[2]Spark generator at his home.

[3]ASTRONOMY I; II (Ginn 1926).

[4]Fund for Astronomical Research.

[5]S. Rosseland, THEORETICAL ASTROPHYSICS (Oxford, 1936).

[6](with Katherine C. Gordon) APJ 97 (1943) p. 311.

[7]APJ 111 (1950) p. 454.

[8]Flagstaff station of the Naval Observatory.

[9]PASP 68 (1956), p. 125.

[10]PSAP 71 (1959), p. 126.

[11]Personal movies (16mm sound) of astronomers made by the Krons.

[12]APJ 103 (1946), p. 326.