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Oral History Transcript — Dr. Ira Bowen

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Interview with Dr. Ira Bowen
By Charles Weiner
At Mt. Wilson & Palomar Observatories Pasadena, California
August 26, 1969

open tab View abstract

Ira Bowen; August 26, 1969

ABSTRACT: Family background; undergraduate work at Oberlin College AB 1919; graduate work on vacuum spark spectra under R.A. Millikan at University of Chicago 1919-21; at Caltech as Millikan’s research assistant: cosmic ray work (1922), vacuum spectrograph (1923); determination of Bowen ratio leading to PhD thesis 1926; nebulium research: origins of interest, conclusions, follow-up at Lick Observatory-- determination of H as most abundant element in stars (1934), development of image slicer 1938, observation of “forbidden lines;” research results channel interests closer to astronomy; teaching positions and duties at Caltech; war work and disruption of research; postwar seminars relating nuclear physics to astronomy; appointment as Director of Mount Wilson-Palomar Observatories 1946, priority of constructing 200 inch Hale telescope, administrative details. Session II: post-war organization of Observatories, administrative committees, funding, division of project time and organization of staff, senior staff members Hubble, Baade, and Adams, incoming staff; achievements in astronomy: final constructing, testing, and setting into operation of 200 inch, developing auxiliary equipment, building Schmidt telescope, revision of distance scale of universe, rise of radio astronomy; communication within field; public interest in astronomy; personal research after retirement in 1964.

Transcript

Session I | Session II

Weiner:

I’d like to start where we indicated would be appropriate at the end of our last session, which was about a year ago. That took you up to the beginning of your directorship of the Mt. Wilson and Palomar Observatories. I think at that time we had discussed your work in the 1930s on the Policy Committee which met regularly and frequently to plan the telescope. You sat in with the Construction Committee, the people who were actually building parts of the telescope. You described that in your last interview as well as the ease of cooperation with Caltech and the informal way it was handled. We didn’t go into the details of how it was set up. You also mentioned the sessions that were held informally at your house, I believe, where Willie Fowler and others on the physics side and especially those on the astronomy side concerned with the spectroscopic work, got together on questions of abundances, and that this was very influential in Willie Fowler’ss4sequent work. What I’d like to do now is to ask you about the situation at the observatory (I guess it’s appropriate to call it “observatory” then, since only one was really functioning) when you became director. It seems to me there were several problems of post-war reorganization of staff, of the problem of phasing out of war work, and resuming work on the 200-inch.

Bowen:

Yes. The staff of the old Mt. Wilson Observatory had largely been taken on by Dr. Hale from 1904 to 1920. The result is that most of those were getting towards the end of their career. Actually, when I took over in ‘46, about 80% of the staff were older than I was; and, of course, that meant that they were retiring rapidly in the next few years, and that one of the major problems was to replace this staff. Also, the observatory, of course, had been constructed in that same period, between 1904 and 1920; and naturally a good many of the instruments had become obsolete or obsolescent anyway, and consequently needed to be updated or replaced with equipment in line with the new equipment which we were developing at Palomar. Those were the two main problems outside of just learning how to run an observatory.

Weiner:

You had never had experience with any supervisory function of a large group?

Bowen:

No. During the war Caltech was running this big rocket project, and I was in charge of the exterior ballistics part of it, which meant developing a lot of instrumentation, special cameras and so on, for following the rockets and determining their exterior ballistics. There were such factors as every now and then a rocket would blow up, and you wanted to know: was this due to unusually high pressure developing or was it due to a failure of the metal parts. And in general this could be done by determining whether there was an increase in acceleration just before the explosion. That’s just an example of the sort of thing that we were trying to determine as well as the overall functioning of the rockets, by determining the way they accelerated and the way they departed from the straight course they were supposed to follow, which was done photographically using, as I say, special cameras which we developed for the purpose—largely of the motion picture type.

Weiner:

It seems to me you discussed something of that the last time and some of the subsequent applications of these cameras. But you had worked with a group and had a responsibility within it, but you had not had responsibility for a permanent research organization.

Bowen:

No.

Weiner:

So in that sense, as you pointed out, that was the most difficult challenge you faced. But was there a clear program already formulated before you came relating to the work on the instruments, the ones that were obsolescent or getting that way, at Mt. Wilson?

Bowen:

Well, of course, as far as the actual observing programs go, we have always given the different staff members a pretty free hand to carry out their own programs; and this was especially true at that time, because, as I mentioned, these were all senior staff members that had been with the observatory most of their lives and in general knew their own programs much better than I did. So naturally there was no attempt to dictate to them how they should handle things. The main problem, of course, was if there should be a conflict of interest between two programs using a given instrument or in building new instruments. Those had to be settled, of course. But in general the group had been used to working together for a good many years, so there were very few problems of that sort up here.

Weiner:

Nevertheless your position must have been a little bit difficult because of the difference in age, the fact that you had moved over from another field and had not come up through the observatory. Was this any handicap to you or did it influence the type of leadership you exerted at first?

Bowen:

I didn’t feel that it did, because since I had been here in Pasadena, had known all of these people for a great many years and they had known me, and I think I can say we all respected each other; and most of those being older people, they weren’t thinking too much in terms of aggressive new projects—-it was largely finishing up the projects they already had underway, so there wasn’t too much of a problem there. That is, I tried to give them a very free hand to go ahead and work their own programs as they wanted to and interfered, as I say, only when there might be a conflict between two programs. So that on the whole things went very smoothly.

Weiner:

Did everyone come back from the war and resume their positions? I read in one of the early annual reports that I guess all but one had returned.

Bowen:

Yes. I think the only one was Dunham. Dunham was a rather unusual character. He came from a well-to-do family. His father was a doctor and insisted he become an M.D. So he took his M.D. Then when he got through, he said, “Now I’m going to do what I want to do,” and took a Ph.D. in astronomy. Well, he had always been rather torn between those two fields, and he rather wanted to start here quite a lot of biological work, particularly involved in the application of optics to biological problems. And he came in with that proposal. Well, it happened there were some personal problems. He was an exceedingly aggressive fellow and it was realized that if he tried to bring that sort of thing into the shops, there would be a good deal of conflict; so that we told him we’d be very glad to have him come back as an astronomer, but that we couldn’t permit this other sort of thing to be done in our shops. And as a result he decided to go elsewhere. Actually he went back and took a refresher course in medicine and then worked at the University of Rochester for quite a while. Now he’s gone back to astronomy and is in Tasmania building a telescope over there.

Weiner:

I noticed in one of the annual reports that in 1947 he resigned to carry out investigations in the field of bio—physics. But thought that the reference I had made was an earlier one to one of the staff who was on leave during the war and didn’t come back in any way.

Bowen:

Well, Stromberg did resign, however, just before came. He was a rather mystically inclined fellow and was doing a lot of semi-religious writing rather than astronomy, and think Dr. Adams rather encouraged him to retire a little early on that account. That was the only other case that I remember offhand.

Weiner:

Had the others been involved in similar war work? That is, in your case you were involved with optics. How about the other people on the staff?

Bowen:

Well, Olin Wilson and Bob King had come over to Tech and were working on the rocket project. Then there had been a number of rather minor optical problems carried on in the shops here. However, Dr. Bush, who was, of course, head of OSRD, didn’t feel it was appropriate to give to his own institution (he was also head of the Carnegie Institution at the time) some of these major projects. And so while they had enough to keep the shops busy, they didn’t take on any of these major projects here at the observatory. Actually they were somewhat under Dunham’s general direction, Dunham was chairman of this 12.1 committee, believe, of OSRD.

Weiner:

But generally the people were not here. They were on leave. They either went to Caltech or perhaps some of them to the Radiation Laboratory or something of that type.

Bowen:

Well, most of them were here, You see, most of these were older people, people 50 or beyond. It was a little hard to get into new projects. So they continued here. The one person that really continued in his work and did a tremendous amount of it—and that’s really where he made his reputation—was Baade. Baade, of course, had never taken out American citizenship, and consequently he was technically an enemy alien and was supposedly confined, I think, to within ten miles of his home; but special arrangements were made so that he could periodically go to Mt. Wilson. And since most of the other people were in war work, either here or in Caltech, he had quite a substantial amount of the time of the 100-inch; and it was during this period that he developed the ideas of Population I, Population II and things of that sort, which was one of the main things that came in after the war.

Weiner:

I imagine the wartime blackouts helped the scene a good deal too.

Bowen:

Yes. Due to the blackouts here—you see, we’re so near to the coast that they put nightcaps on all the street lights and everybody was supposed to pull their curtains down as low as any light in the house— it was nearly as black on Mt. Wilson as it had been 50 years ago. So he was able to do a great deal of very good work with the 100-inch at that time, even on direct photography.

Weiner:

That work has been described I think adequately. At the end of the war during the period that you took over, people came back. Was it a very difficult period in getting started up again? First, there was the question of people being away. Secondly, there was some war work being done here still after the war—some government work.

Bowen:

Yes. It was phased out pretty quickly, though.

Weiner:

And then starting up on the 200-inch must have been a problem, too. It seems to me there were two things involved there: one is formulating plans for a joint operation of the two institutions; and then the other is actually resuming construction, which I assume had come to a complete halt in every phase of the work.

Bowen:

Yes. Of course, the optical shop and the instrument shop at Cal- tech had just closed down as far as any construction work on the 200-inch was concerned. They were running two and three shifts on war work at the machine shop and to quite an extent the same thing at the optical shop, so that they were essentially closed down as far as scientific work. I didn’t have too much to do with .getting those going again, because Dr. Anderson, who was executive officer and was the one who actually handled all the details of the 200-inch construction (these committees were largely advisory on broad policy matters), was still there and continued up to about 1947 or ‘48. That’s J. A. Anderson. And consequently, he, along with Rule, who was the other engineer that came back, handled getting the shops going again and getting the job finished up. So that I didn’t have too much responsibility until the mirror went to the mountain. Then Dr. Anderson, who was about 70, had a heart that was causing him quite a little trouble, and it was very unwise for him to go to the mountain; so my responsibility came then in taking over the tests and the adjustments of the instrument on the mountain after it left here. Oh, he wanted some checks on the final figure of the mirror. Using a different method than he’d used, I ran a final test on it down here just as a check on his value. But that was a rather minor matter. The point when I really took over was testing the mirror after it went to the mountain. One of the problems there had been that here at the laboratory we were only able to test the mirror tipped up on edge-—that is, with its optic axis horizontal. The mirror was supported with 36 supports distributed over the back. However, the outside row of supports was some 12 to 18 inches inside the edge. And since this turned out to be a very flexible mirror, we were quite concerned that When we tipped it up with the optic axis vertical, that the edge would droop. And if that proved to be the case, then we would have to pretty well refigure the mirror to take that into account. So in the figuring down here, we deliberately left the edge something like a wavelength high, thinking that it probably would droop when it got up there. On taking it to the mountain, however, that proved not to be the case. Of course, one of the first things we had to do in making these tests was to make sure that the support system was functioning properly. We used the Hartmann test, which is a very precise test, and a rather standard test for testing any large mirror. And we started out by taking Hartmann tests working on a star with the telescope pointed vertically, then moving it over east to, say 60 degrees from the zenith, and south and west 60 degrees to the zenith, and then comparing the figure in these different positions. And we found that it was coupled with the support system. There apparently was hysteresis in it in such a way that we would get differences between these; or we would find, for instance, if we went to 30 degrees from the zenith, we got one figure if we approached it from a smaller zenith angle, indicating there was hysteresis in the support system. So after very thoroughly investigating the mirror, we decided that the friction was too great in the support system, and we would have to do something about it. The friction was about one per cent in those original support systems. So the lever system, which is part of the support system, was redesigned and rebuilt in the summer of ‘48, believe, and cut the friction down from about one per cent to less than one-tenth of a per cent. This got rid of our problem of hysteresis; so that in going to a given position, we got the same figure. The next problem was, however, that we got a different figure in the zenith than we did at a large zenith angle. Of the 36 supports, we defined the mirror by locking three of them at the extreme corners. And we found that as we went from a large zenith angle to the zenith, those three points punched up high, indicating that the rest of the support system was not carrying enough weight; and consequently the three fixed ones were carrying more than their share, Well, that involved a certain amount of change in the weights on them so that they exerted more force, and that got rid of that, Then we found that rather strangely as we went from a large zenith angle to the zenith, that instead of the edge drooping, it went up— actually went a little higher. Again, on further investigation, we found that also at the same time the focal length lengthened as we went to the zenith, on the order of a millimeter. This was presumably due to the fact that the inner ring of supports was carrying too much of the weight, and the outer ring too little, which meant that you punched the center up with respect to the outside as you went to the zenith. When we again corrected that so that there wasn’t a change in focus, we found that the rising of the edge as you went to the zenith did not occur——in fact, it drooped very slightly, but only by about one-tenth as much as we had feared it might. Which meant that we were left with a mirror which was high on the edge. We then carried through a lot of tests on thermal effects and found that we could get better thermal behavior by insulating the edge. This was done by deliberately closing the dome up, heating it as hot as we could get with all the power we had in the dome and then suddenly opening it up and observing the behavior of the mirror for a few hours afterwards. As a result of all these tests, we found, as I say, that the edge was high and that there were also a few other minor errors on the surface, which would have to be corrected. Before doing this, however (and this was in the spring of ‘49), we decided to use the telescope a little to get a check by the actual users that we were having a little trouble from this raised edge. So in the spring of ‘49, Hubble and Baade and one or two others did make two or three runs, taking direct photographs with the mirror as it was at that time. Then in the summer of ‘49, we took the telescope out of operation, and Hendrix did a refiguring job taking down the edge and one or two other points that our more elaborate tests that we made on the mountain showed needed correction. This refiguring was done by my going up to the mountain, running a series of Hartmann tests, and also taking photographic knife-edge tests of the mirror, with a camera focused on the mirror behind the knife edge. Then after these were brought down to Pasadena and measured and assessed, they were turned over to Hendrix, He would go up and do a little figuring. Then would go up and take another set. This continued for four or five months in the summer of ‘49, Hendrix had spent about nine hours total figuring on the thing. Four or five months were taken to make the tests, because in making these tests, seeing had to be fairly good. I would go to the mountain and often have to wait for several days until we had both clear skies and good seeing and the tests could be run and brought down here; it would then take a few days to assess them. So that Hendrix would go up roughly once every two weeks and would polish maybe for an hour, Then another set of tests would be made. Then there were a few more thermal tests made, and the thing was put into operation as far as the telescope itself—that is, for direct photography—in the fall of ‘49.

Weiner:

Bur prior to that time, about 150 photographs had been taken? I thought I saw that—as part of the test program.

Bowen:

It may have been. I’ve forgotten the exact number now.

Weiner:

Did you live there on a steady basis when you first went up?

Bowen:

Oh, yes.

Weiner:

For how long?

Bowen:

The monastery was running at that time, had been running because of construction work right along. The monastery is the little place up there where we live when we’re on the mountain. It has a cook and somebody to look after the rooms. It’s known as the monastery because in general we’re very strict about visitors, and that includes women—largely because when you’re on the mountain, you’re working very hard and working at night, you come back usually at five o’clock in the morning, sleep through till noon, and you can’t have somebody in the next room getting up and taking a shower and so on right in the middle of that. So we’ve always been very strict about any visitors there who are on another schedule than the observers.

Weiner:

That name was first introduced on Mt. Wilson.

Bowen:

Yes. But for much the same reasons. An astronomer on the mountain is usually working pretty strenuously. Take at Palomar. You leave here at eight or nine o’clock in the morning, get there at noon, spend the whole afternoon getting your equipment adjusted, and then you observe all night, which means about a 20 or 24-hour day. And even after that, if you go to bed at, say, five in the morning and get up at noon, often you have then adjustments for the next night, your plates to develop that you took the previous night, and then you work through till morning. So it’s a pretty strenuous existence when you’re on the mountain. You just can’t tolerate any disturbances.

Weiner:

How long a period of time was involved in the initial period of testing the mirror, testing the support system and so forth, when you were up there continually? And how large a group was up there with you?

Bowen:

Well, of course, there was always somebody. That is, when we operate a telescope of that kind, there’s always at least two people present—-namely, the astronomer and the night assistant. During that period, since there were a great many problems, Byron Hill, who is the engineer who had been in charge of building the telescope, and who was later (until he retired just two or three years ago) mountain superintendent, would often operate the telescope for me when was running these tests. In those days there were naturally mechanical problems cropping up every now and then, and he was the best person available to know what to do about it if they did crop up. So there were usually the two of us present.

Weiner:

What about these extensive corrections in the support system that had to be made?

Bowen:

Those were made here, of course. That meant a certain amount of rebuilding. And they had to be made in Pasadena.

Weiner:

These were individual units that would be rebuilt?

Bowen:

Rebuilt, yes.

Weiner:

But the refiguring, of course, was done there. It was originally aluminized as soon as it came…

Bowen:

Yes, But that had to be taken off for the refiguring.

Weiner:

Now, this was the first time that the testing of a large mirror had been done in place actually on the telescope. Is that so?

Bowen:

I think that is correct. That is, think other telescopes had been tested, but this is the first time that the final figuring was based on tests on the telescope.

Weiner:

This had great advantages.

Bowen:

Yes, One of the things you run into is that as you get to bigger and bigger mirrors, they become very flexible. You see, the flexibility of a mirror varies as the fourth power of its diameter and inversely as the square of its thickness. So that if you keep the diameter to thickness constant, the flexibility, or more specifically the flexure under its own weight, goes up as the square of the aperture. For instance, in the case of the 200-inch, it was necessary that all of these supports apply the proper forces to an accuracy of better than one-tenth of one per cent. With a smaller mirror that isn’t true. Well, it’s rather obvious that as you get to these big mirrors, it’s almost impossible to design and adjust them here with that accuracy. You have to wait and actually test them in the telescope, and the telescope is about the only place where you can actually turn it into all kinds of different positions and measure the effect. Some optical shops do have a vertical tower in which they can test it with the optic axis vertical, but they still don’t know that the support system is operating properly. For instance, if we had tried to make the correction that Hendrix finally did before we’d run through all these tests… For instance, this case of the three fixed points punching up; we would have simply ground those down; and then when we got it properly adjusted later, they would have been hollows, which would have meant refiguring the whole mirror.

Weiner:

Or if you had done the figuring around the edge to what it should have been before putting it up, you would have been stuck with…

Bowen:

Well, we just didn’t know what it should have been actually. So that I’m quite convinced that as you get to these very large mirrors, it is essential to do at least the final figuring on the basis of tests in the telescope, because that’s the only place in which you can move into all these positions, make sure that all support systems and so on are functioning properly.

Weiner:

Was the basic structure intact on the mountain before the war? Here I’m thinking of the horseshoe and all the mechanisms completed.

Bowen:

Yes. That was ‘37 or ‘38, I believe, that that was completed.

Weiner:

The dome and everything.

Bowen:

The dome was completed, and actually it had been operated with a dummy concrete mirror. You may have seen it.

Weiner:

In the little museum.

Bowen:

No, that’s just a model of the mirror. It’s lying just outside of the big door to the west. It’s still lying there. It was reinforced concrete made to have the same weight as the mirror. Of course, you couldn’t operate the telescope without that sort of thing because it would be top-heavy by 15 tons or so, which would have put undue strains on the gears and so on if you tried to operate without having a corresponding weight present. But this was completed a couple of years before the war and was operated off and on just to keep grease from getting stiff and so on. Even during the war it was operated just for that purpose.

Weiner:

You had gone down then as part of that committee. Had you gone down during the ‘30s?

Bowen:

Yes.

Weiner:

It seems to me that this is a tremendous responsibility that you had just at the same time as taking over an existing observatory with a large staff.

Bowen:

You see, I took over on January 1st ‘46, whereas, as I mentioned before, Anderson was then handling the 200-inch. It was nearly two years later, at the time the mirror was taken up the mountain, which I believe was November or December of ‘47, that I took over responsibilities on the mountain. So that I had a couple of years to get used to getting things under control, if you wish, down here.

Weiner:

The trip to the mountain was November 18th and 19th, 1947. Did you go along on that trip?

Bowen:

Yes. They started out from here at three o’clock about in the morning from the optical shop, because they wanted to get out of the Los Angeles area before traffic built up, because the truck they were carrying it on naturally had to be wide enough to take about two lanes, therefore rather seriously blocking traffic. And the plan was to go to Escondido that day and then bring it up the next morning. I didn’t accompany that part, although Rule did. The plan was that Dr. Mason, Dr. Adams and I think Dr. Anderson and I were to meet the thing on the second day on the mountain. We started out bright and early to get there, as I remember, planning to reach there shortly before noon. The mirror was to get there at one or two o’clock that afternoon. We started out; it began to rain; and we went around the back way through Warner Springs so as not to get stuck behind the mirror, because the plan was to close the road up the mountain that day. And we went up by another road from Warner’s Hot Springs. We got to the top of the mountain, which is about five miles short of the observatory, and were surprised to find there were no policemen there blocking the road. And since it was raining and misty, we decided that probably Rule, who was in charge of the actual caravan, had decided it was too risky to go up the mountain with wet pavements. So we decided we’d go over to the dome anyway and phone down to Escondido. When we got over to the dome, the mirror was there. It had gotten up a couple of hours ahead of schedule.

Weiner:

That must have been a pretty tricky journey. I’ve seen some descriptions of it. The road was pretty slick. There were some films of this, too. And then it was immediately transferred from the truck to the aluminizing tank?

Bowen:

Yes. I believe that was the case. I didn’t stay over to see the aluminizing, It may have been put in the telescope first just to make sure that fittings were all right and so on. I’ve rather forgotten the details of that.

Weiner:

This was a new aluminizing process, too, developed by John Strong.

Bowen:

Yes, although it had been used on the Mt. Wilson telescopes before.

Weiner:

For realuminizing, you mean.

Bowen:

Well, the Mt. Wilson telescopes had been aluminized. The first one to be aluminized was the Lick 36-inch, and then after that the Mt. Wilson ones were aluminized; so that this wasn’t by any means the first mirror to be aluminized.

Weiner:

But was this evaporation process a different process?

Bowen:

No, all of these were the evaporation process. They were all by this process developed by Strong, which was developed, however, as part of the overall project. That is, Strong’s development was financed by the 200-inch project.

Weiner:

In other words, he was brought out here especially for that. Or did he do his work at Hopkins or wherever… ?

Bowen:

No, it was done here. He had come here as a National Research Council fellow, and then he was kept on 200-inch funds, and he developed the process, using small mirrors. Then they felt it was too big a step to go to the mirrors for the 60-inch and the 100-inch; so they built a 40-inch tank which would take the Crossley 36-inch mirror at Lick. And that was the first actual astronomical mirror of any size aluminized. And then having had success with that, they built a 108-inch tank to handle the 60-inch and the 100-inch at Mt. Wilson. That had all been done before the war.

Weiner:

The work on the auxiliary equipment must have started when you came in ‘46. Or had some of it already been underway?

Bowen:

Well, they had started as sort of a fill-in job in the optical shop, the optics for a spectograph duplicating on a somewhat larger scale some of the spectographs used at the Cassegrain focus of the 60-inch and the 100-inch. However, by the time the war was over, the Schmidt camera was in. They had succeeded in ruling larger and very efficient gratings, and consequently we decided that it was foolish to go ahead and complete these prism lens spectographs that had been designed and some of the optics built as fill-in jobs. And so we junked this; went ahead and built a new nebular spectograph for work on the velocity of galaxies and thin like that, more or less duplicating one which had been built just before the war at Mt. Wilson. Minkowski was quite largely responsible for the design of that spectograph, although, as I say, it was quite largely a duplicate, simply a little enlarged, of the one at Mt. Wilson. Then, starting almost immediately after ‘49, we started working on the big Coude spectograph. There it was realized that particularly for the high dispersion work, if we simply duplicated the spectograph at Mt. Wilson, we would get a little wider spectrum, but we couldn’t go any fainter than we did with the 100-inch, and consequently we just felt we couldn’t tolerate that; that is the 200-inch would be essentially no better than the 100-inch as far as large-scale work. So we did some rather serious figuring on things and made the rather drastic decision to go to a mosaic of four gratings in order to get a 12-inch beam instead of the 6-inch beam which had been used at Mt. Wilson. This was made possible largely because H. D. Babcock had taken over from Anderson the ruling engine here at Santa Barbara Street and had been very successful in ruling some large, about 5 by 7, gratings with a very high concentration of light in one order. He was able to rule four practically identical gratings of this size, which were then put together as a mosaic. We had to develop methods for adjusting them and keeping them in adjustment. And then there was a question of going ahead and using Schmidt cameras. These had been introduced at Mt. Wilson by Dunham before the war at the Coude there. However, he had introduced only the long-focus ones, and it seemed desirable, in addition to the long-focus ones of 12 feet and six feet and three feet focal lengths, which more or less corresponded to the dispersions on Mt. Wilson, to go to even shorter ones. And rather careful calculations showed that one could go down to 18-inch with the Schmidt camera and a 12-inch beam without running into serious aberrations. And then we developed the aplanatic sphere, which enabled us to push still further down to about eight-inch focus. These were constructed between ‘49 and about ‘52, Hendrix, of course, doing the optics on them, There Dr. Olin Wilson and I went into partnership to get them into adjustment and use them. Due to the fact that we were using quite a lot of pretty novel ideas in the thing, we felt that we wanted to get the thing going pretty thoroughly and under control before we turned it over to a large number of different observers. So that Dr. Wilson and I took most of the light -of-the-moon time, when you do spectroscopic work, from about 1950, when the first camera was available, until ‘52. In that period we, however, took quite a few plates for other observers—notably Dr. Merrill, who was retiring in ‘52 and consequently would not be able to use the instrument, Also, he was rather badly crippled up with arthritis’, so he quite appreciated having the plates taken for him, The longer focal-length cameras, which more or less duplicated the dispersion of the spectograph at Mt. Wilson, gained us about what we had expected of a magnitude or two by going to this large beam in a mosaic grating. The short cameras, however, because the beam was very much larger than anything that had been used at Mt. Wilson, gained us very much more—some four or five magnitudes—and were used a great deal in the early stages, because they opened up quite new fields, For instance, it was with these cameras that they were able to get a spectra of some of the stars in globular clusters and show that the original classification of these stars was wrong, which had been done on the basis of very low dispersion which did not show the metallic lines. With the medium dispersion, with which we succeeded in reaching these very faint objects with the Coude here, it was found that the metallic lines were present but were very weak and were simply an indicator that in these globular clusters the abundance of the metals was only one or two per cent of that in a good many other stars, which led again to quite a clarification of the properties of the Population I and Population II stars.

Weiner:

This was one of the first major results of the work at Palomar, wasn’t it?

Bowen:

Yes, it was one of the early ones. Of course, Baade and Hubble had been using direct photography even before this spectroscopic work started; so that it was one of the first results as far as the spectroscopic observations go. Well, that covered the introduction of the spectroscopic equipment there. The other field that was beginning to develop rapidly after the war was the photometric work. Shortly before the war, Stebbins, really starting in 1930, had introduced photoelectric measurements which gave fairly accurate quantitative magnitudes. But before the war, this was limited to fairly bright objects, because the photoelectric cell wasn’t very sensitive, and using an external amplifier, the noise from the amplifier limited the faintness of objects that you could measure. During the war, I believe, however, the photo multiplier tube was developed, which caused all of the initial amplification to occur actually in the tube and thereby cut down most of this noise. This immediately made it possible to go to very much fainter stars, In fact, with some of the later tubes it was possible to go to stars as faint as one could photograph and make quantitative measurements. It was realized that this was very important, because the magnitude scale was the basis for all the distance measurements that Hubble and Baade were making of the galaxies and things of that sort. The whole scale of the universe depended on these. And there was indication that the original magnitude scale, which had been determined photographically by Seares and others, was rather seriously in error. So there was a great deal of pressure to start something going on a redetermination of the whole magnitude scale, starting with the polar sequence and then going to various selected areas. We first brought Stebbins and his assistant Whitford out for several sessions with the 100-inch and also the 200-inch. However, there was so much of this to be done, and so much of our work depended on it, that it was realized we should have someone at the observatory who could do this in cooperation with our own astronomers. We had quite a discussion on how we should proceed, because there were very few astronomers in the country who had had any experience with a lot of this electronics work; and, on the other hand, physicists, of course, had very little background in astronomy. After a good deal of discussion, however, we decided that we could probably train a physicist in astronomy better than we could train an astronomer in electronics. And consequently we went to Caltech and got one of their very good young graduates who was especially strong in instrumentation—namely, Dr. William Baum—and he joined the staff, developed, working with Stebbins and Whitford somewhat, photometers using the photo—multiplier tubes and so on; and then in cooperation with the other staff members tackled a good many of these problems. It proved very important, however, because they found that the magnitude scale at the very faint magnitudes, which is what is used in determining the distance of galaxies such as Andromeda was in error by about a full magnitude, which made an error in the distance, of course, of about 602g. That was one of the big factors which came in the increase in the distance of Andromeda from 700,000 light years, as originally given by Hubble, to 2,200,000, which is now the best estimate.

Weiner:

This was done by ‘5l, ‘52?

Bowen:

I think this was later than this that this was all carried out-through the ‘50s.

Weiner:

The Population and II work had changed the entire distance scale of the universe—wasn’t this in ‘51 or ’52…?

Bowen:

Well, the Population and Population H really developed during the war, That came from Baade having the 100-inch practically to himself throughout the war.

Weiner:

I was thinking of the announcement at the IAU meeting in Rome in ‘52 relating to the fact that all distance scales would have to be revised by two and a half times or something like that.

Bowen:

No. As a matter of fact, this final 2,200,000 was announced in ‘63 or ‘4. Now, there were a lot of factors in it, One was this magnitude scale. Another was that the scale of the Cepheids—there was an ambiguity there as to populations and so on of the Cepheids.

Weiner:

That, I think, is what I was referring to for ‘52.

Bowen:

Well, I think the problem was realized in ‘52—that there was something radically wrong. But the final solution, carrying out step by step these different things, was only finished up in the early ‘60s.

Weiner:

Getting back to the construction, was the work on the 48-inch Schmidt proceeding (and the 18-inch for that matter) before the war?

Bowen:

The 18-inch was done before the war—was in operation before the war, I believe, The 48-inch, however, may have been started before the war, but certainly the optical work was done after the war. Hendrix did that after the war, and did it very skillfully. And one rather interesting thing: we were pushing the speed of that to the very limit; we knew we would be in trouble if we allowed the ultra-violet through. So we deliberately used glass that was opaque to the ultra-violet. And the simplest way to do that was to use ordinary window glass. Hendrix went over to the largest plate glass company in Los Angeles, hired their crew for a weekend, and then set up…Of course, the trouble with plate glass is that it often has bad stria—namely, an arc with a big white paper behind it and then brought the pieces of glass in, and that allowed the light to go through; and from the shadow patterns you can determine whether there is any stria. He went over their whole stock of glass for the proper thickness and selected two pieces, one of which was used in making the 48-inch corrected plate.

Weiner:

Probably the cheapest piece of optical glass on record.

Bowen:

Well, it cost quite a little to hire the crew to select it.

Weiner:

I imagine, but the materials themselves. Well, when did the 48- inch go into operation? Do you recall?

Bowen:

In ‘49, remember that, because as you remember, the first big project for that was the National Geographic Sky Survey. We were planning a little celebration with some of their people and Hubble, who was one of the leaders in planning the thing. Unfortunately Hubble couldn’t be there, because he had his first heart attack just before that. He was fishing, in Colorado when he had this heart attack.

Weiner:

Talking about that occasion and the celebration, what about the circumstances of the dedication of the 200-inch? Now, this was in 1948, and it was followed a month later by a scientific meeting. I’d like to know about both of them.

Bowen:

Well, it was planned that year to have a meeting—I think it was a joint meeting—of the American Astronomical Society and the Astronomical Society of the Pacific here in about the end of June ‘48. Because of that, we decided to have essentially two dedications: the first one, which was the first week in June, for local people, and in particular the California Institute has been supported, of course, by a great many local people. They set up this associates program in which local people contribute $1000 a year, and in return Caltech tries to put on various parties for them, scientific talks and things of that sort, So this first dedication was more or less set up for various local V.I.P.s, if you wish, of that type—people who supported the Institute and local dignitaries, And this was set for the first week in June. And very few astronomers were invited to that. The local faculty—Caltech faculty—were, but it was largely local people. Then in connection with the joint meeting of these two astronomical societies, an expedition was planned down there; and a second dedication, with the emphasis on the scientific side, was then given in, believe, the last week in June.

Weiner:

It may have been July already by that time.

Bowen:

Then there was actually a third celebration along in August, because thanks to the Congressman of that district a Palomar three-cent stamp was gotten out; and we had somewhat of a celebration in connection with that. It was rather interesting. Palomar is a fourth—class post office, which means that the post mistress gets the value of the stamps she cancels as her salary. Of course, there’s always the problem of the first-day cancellation of a new stamp, and the post office department figured that there would be some 300,000 stamps cancelled, which would be quite a sum. So the local post office was promoted to a third-class post office the week before, and a week later it was demoted to fourth- class again. And all of the letters were stopped in Oceanside, which is the nearest town of any size. They hired a lot of extra clerks to handle them, But the cancelling machines were sent up to the dome, and the actual cancelling of the stamps was made in the dome—the first day of cancellation of the stamps, which stamp collectors are always much interested in. In connection with that, the Post Office Department sent out a deputy postmaster general or one of the high officials, and we had a meeting there attended by several hundred people in which Lee DuBridge talked and I talked and this representative of the Post Office Department talked and so on. And we put on a demonstration of the telescope and then they cancelled stamps.

Weiner:

All of these occasions were by daylight?

Bowen:

Yes, all of these were afternoon affairs.

Weiner:

On the first dedication for the associates and the others, did everything go off well? It was still early in the game.

Bowen:

Yes, everything went off well. You may have seen some of the pictures of it.

Weiner:

I’ve seen the booklets that were issued then.

Bowen:

We had a thousand people seated on the main floor of the dome, with a speakers’ stand to the west. We could get in a thousand chairs, we found, on the main floor without using the balcony; and they were practically all filled. Our thief concern was the fact that some oil would leak out onto the people; and in those early days there’d been various things. You’d turn the telescope, and you’d hear a nut come trickling down or something like that. They were afraid something like that might happen, because of course the crowd had to be seated immediately under the telescope.

Weiner:

Did the telescope itself function properly other than avoiding soiling the people with oil? Did everything go off?

Bowen:

Yes, everything went off very well. You probably have seen the program.

Weiner:

Yes, I have a copy here as a matter of fact.

Bowen:

So you know what speeches were given and so on. As you notice, my main function was to sort of introduce the telescope and tell a little bit about how it operated and so on.

Weiner:

And that meant to give an actual demonstration of it.

Bowen:

Then we followed it with a demonstration, which Rule operated.

Weiner:

I checked while we were talking before that the scientific session was on July 1st 1948. But then followed a long period of testing, which you’ve described. Meanwhile, back off the ranch, here—you were working on plans for a joint operation by Carnegie Institution at Washington and the California Institute of Technology of the two observatories. And we started yesterday, as background, differentiating the various committees, and you pointed out that there were two sets of them—some of the committees that had functioned prior to the official coming into being of the jointly operated observatories, and then a new set of committees. Maybe we should review those briefly.

Bowen:

Well, while the construction was continuing, the top committee was the Observatory Council, which was made up largely of trustees, although Dr. Hale, of course, was on it. He, of course, was a trustee of Caltech, and I think Dr. Adams was on it. That, however, ceased when the joint operation began. Likewise the Policy Committee was the top scientific committee and was made up of Mason as chairman, Hubble and Adams from the Mt. Wilson Observatory, and Tolman and myself from Caltech. This met once a week and spent most of the afternoon discussing things. For instance, Anderson would often bring in a report showing the last tests of the surface of the mirror, and major scientific decisions as to what should be done were made by this committee. Then there was a Construction Committee—of which I believe Anderson was chairman, and Pease, and Sinclair Smith until his death, and two or three of the other engineers were on—which handled largely mechanical details, although the members of the Policy Committee were always welcome to sit in with it; and I often did. Well, these were the committees doing the construction. With the beginning of joint operation, the agreement between Cal- tech and the Carnegie Institution provided for two committees. The main administrative committee was known as the Observatory Committee, of which the director was chairman; and then it was to have three members from Caltech, three members from Carnegie. Actually, as it started off, as far as personnel, this was largely a continuation of the Policy Committee, except that took over as chairman; and Mason was kept on and Tolman was kept on from Caltech, and Adams and Hubble and were kept on from Carnegie. Then, however, as Tolman died shortly after this, and as Hubble dropped out and Adams dropped out and so on, they were changed to other members of the staff. Those names, of course, can be gotten from the annual report. I wouldn’t remember the exact years that we changed these.

Weiner:

Bacher came on later and later on Carl Anderson came on.

Bowen:

In general, due to the fact that the graduate school of astronomy was part of Caltech, it was felt that in order to correlate the two, the chairman of the division of physics, astronomy and mathematics should also be a member of this committee, so as to correlate the research of the observatory with the graduate school. Then there was also another committee known as the Research Committee of which Hubble was chairman. However, Hubble was never too much interested in committee work, and so to the best of my knowledge it only met once for about a half an hour, and has since been discontinued, with the feeling that probably the other committee could take over those responsibilities as well.

Weiner:

By the other committee, you mean the Observatory Committee?

Bowen:

Yes, the Observatory Committee could take over those responsibilities as well. The agreement between the two institutions, which I don’t need to follow in detail, has proved a very effective agreements ft was very informal as it could be because of the fact that they were both private institutions. Just as one illustration of how informally they could be worked, the agreement provided that Caltech was responsible for the expenses of operation of Palomar and Carnegie Institution of Mt. Wilson, and that each institution should hire as large a staff of astronomers as their finances would permit. However, in operating a large complex of this sort, there are many overlapping functions. One of the early problems that we ran into was the fact that we had to provide transportation back and forth to both mountains for astronomers as they changed and went up for their observing periods and also for supplies—food, instruments and so on. It seemed, on thinking about it, rather inefficient to hire two drivers and two sets of cars, because in general we went to each mountain roughly twice a week. Consequently, after discussing it briefly with the presidents of both institutions, they reached a very informal agreement that Carnegie would hire the drivers and Caltech would buy the cars and they’d go to both mountains, which simply illustrates what you can do with private institutions that you couldn’t do with a government institution. A good many other cases were handled the same way. You wanted special plates, of which maybe a couple dozen of each are needed each year on each mountain, Rather than putting in two orders, one institution would order one batch and they’d be divided up, a part going to each mountain. The next year the other institution would order them, and pay for them, of course.

Weiner:

That has continued pretty much, hasn’t it?

Bowen:

Yes.

Weiner:

There were no complications introduced later?

Bowen:

No.

Weiner:

have a list of the membership of the Research Committee here, the committee which met only once for a half hour. I see that Tolman was on it and Oppenheimer and Baade and Merrill and Seth Nicholson. Did Oppenheimer in any way get involved through that committee or any other way?

Bowen:

I don’t think he did. He came here shortly after the war. He had been at Berkeley, and then it was only a few months or at the most a year or two before he was invited back to Princeton; and so he wasn’t here long enough. And, as say, Hubble was chairman, and Hubble was rather notorious for not caring about administrative details and so on. And he just never called the committee.

Weiner:

What role did Hubble play? It would be interesting to have your recollections of Hubble’s position within the observatory staff and your relationships with him.

Bowen:

Well, you’re raising a rather delicate problem here. Hubble, of course, was by all odds the outstanding astronomer on the staff as far as general reputation goes; and consequently there was often question why he wasn’t Adams’ successor. And think he would in a way have rather welcomed it. However, I think it was realized that he wasn’t really interested in administrative work. He wasn’t willing to do the details of administrative work. That was the reason why, in spite of the fact that he was the outstanding astronomer, that he wasn’t selected. I think one reason why this other committee was set up was to give some recognition to his eminence, happen to know that he was quite disappointed at the way things went. On the other hand, he and had always been good friends, and I naturally made every effort to accede to his wishes, to recognize that he was the outstanding man—that is, in talking about the observatory and so on—and we got along very well. That is, after he got back and got over the initial disappointment. And furthermore, I think that when he had the heart attack he realized that he just couldn’t have handled it anyway.

Weiner:

When was that?

Bowen:

That was in ‘49. That was when he had his first serious heart attack, So that at least from my standpoint our relationships were always good, particularly after this rather initial disappointment.

Weiner:

How about his relationships with other staff, before this time? Was that perhaps another factor in making him not as desirable a candidate?

Bowen:

Well, don’t know, Of course, this happened largely before was here. I don’t know too much about it. I’ve had rather a strong feeling from little remarks made that he, Adams and Merrill and so on didn’t always jibe too well. But it’s more or less just a feeling that I got.

Weiner:

Did he pursue his scientific work in the post—war period? You mentioned that he was one of the first users of the 200-inch.

Bowen:

Well, took photographs, of course, but usually just purely the test things. He was the first one to take a picture with it for serious scientific purposes. Well, one other factor which raised some complications was that Hubble was a little out of it. You see, he had gotten out of scientific work during the war. He was back at Aberdeen, as you know, He had gotten pretty thoroughly out of the scientific work, came back, and Baade, who was a very brilliant fellow, was rather over-shadowing him as far as new work coming out. Actually, Hubble quite largely due to his ill health, and also to quite an extent because of Baade’s rather overshadowing him, didn’t do very much after the war. He did take some pictures and so on. This first use of the telescope was in the spring of ‘49, and was just a trial, more or less trying things out. Then he had the heart attack that summer and was laid up for a year or two. That’s one of the problems with these observatories. They’re six thousand feet. People don’t go to that elevation immediately after a heart attack and so on. The result is that he did in a year or two rather struggle back into things, but it was a big effort for him. Mrs. Hubble would go up, and they would stay at the little cottage. There was a little cottage that we had taken, an old farmhouse that we’d taken over, where they could stay. But it was quite a struggle for him, and he didn’t really get very much, to be perfectly frank, And then, of course, in ‘53 he died. On the other hand, Baade had just opened up this new field during the war of the Populations and H and so on, and he was really going to town; so that from the standpoint of actual product, Baade’s work quite overshadowed what Hubble did.

Weiner:

What about the role of Walter Adams after he retired as director and you succeeded him?

Bowen:

Well, he, of course, retired in ‘46. Due to the fact that was coming up here very green both to astronomy and to administrative work, asked that he be kept on the Observatory Committee, felt he could give a great deal., He knew the men thoroughly. If there were problems with the men, I could go to him and get advice. He had a much longer background in dealing with these men. So he was kept on as research associate of the institution. They kept him on, and think paid him a thousand dollars a year or so for it, for four years after took over. By that time I had gotten things enough under control where I felt I couldn’t very well justify asking them to continue it, but he was kept on for four years.

Weiner:

Did that serve in reality as a helpful transition?

Bowen:

It was very helpful. For one thing, Dr. Adams was a very thoughtful man, and one reason I did it was that I knew he would in no way try to dominate me. You’d go and ask him a question, you’d get a good straight answer. On the other hand, he in no way tried to influence my decisions. He would give me facts, but he wouldn’t try to advise me or urge me to follow certain lines of things. So it worked out very well from my standpoint. He didn’t want an office up here. He kept an office down at the Hale Solar Lab. As you know, the Institution owns this lab down here a little south of Caltech. Of course, Hale was gone at that time. Hale built it largely out of his own funds and then turned it over to the Institution with his beautiful office down there. Adams used that office.

Weiner:

I remember being in the office.

Bowen:

In fact, he used it as long as he could be at all active.

Weiner:

I’m curious about another person, about Max Mason. I’ve followed his career a little bit, the Chicago phase of it, When was it that he came out to California and in what capacity?

Bowen:

Well, you see, he had been, as you know, first at Wisconsin and then president of the University of Chicago. Then he went to the Rockefeller Foundation, He was more or less in charge of the group which was administering from their standpoint this 200-inch project. And then I’m not sure just what the reasons were-—I think he was for one thing getting pretty close to retirement—he transferred out here. You see, Hale had been in charge of this project personally up till ’36. Then Hale’s health failed so that he could no longer continue, and Mason was brought over to essentially head up the project in Hale’s place in ’36—I forget now just what month. He continued on until (he was on the Institute Executive Council and so on) about the time that this joint operation began. See, he was in charge of the construction.

Weiner:

The actual position was chairman of the Observatory Council?

Bowen:

Yes, Then when the Observatory Council ceased to exist and the Observatory Committee took over, again requested that he be kept on the Observatory Committee, because during this first stage, as far as the 200- inch goes, it was completing construction; and consequently he could provide a lot of valuable background. And so he was kept on—oh, for about the same length of time that Adams was.

Weiner:

At the time it was called the Preliminary Joint Management Committee? Or is that yet another committee? The annual report refers to a Preliminary Joint Management Committee with you as chairman; Mason, Tolman, Watson, Adams and Hubble.

Bowen:

I’m not absolutely sure. You could check as to the names o it, But that was the general thing—that those two people were kept on about four years. I forget now the exact names of the committees and so on, There was a phase there from ‘46 when I took over here until ‘48 when the joint operation officially began, and I’ve forgotten now…

Weiner:

I think that was the interim committee which produced the report, and then according to the report there are certain other committees established.

Bowen:

You’ve probably looked that up more recently than I have.

Weiner:

Yesterday, as a matter of fact. But Mason was then on the staff officially of the Institute?

Bowen:

Yes.

Weiner:

I see. So, in other words, he had an appointment there as a member of the Executive Council of that and a salary supposedly from them.

Bowen:

Yes, during that early period he had a salary I know.

Weiner:

Now, one of the other points that I wanted to get into about this period was the funding. You commented in an annual report about ‘51-’52 that “the International Education Board’s $6,000,000 grant received in 1928 and the $550,000 grant from the Rockefeller Foundation to cover increased costs after World War II had all been expended by December 1951, and these funds were enough to finish the telescope and practically all of the auxiliary equipment.” Of course, the point that you were trying to make there was that there would always be a need to modify and perhaps to replace auxiliary equipment to take advantage of what the telescope itself has to offer. Was there any doubt along the way that the funds would run out? Was there any real concern about how you would cope with this situation?

Bowen:

Well, of course, as you just mentioned, the original grant was $6,000,000. We got along remarkably well for a project of that kind. On the other hand, there was a certain amount of loss due to the war, due to the fact that the shops were all closed down and then had to be reactivated after the war—all of which cost money. And also after the war, costs had gone up by probably at least a factor of two over what they were before the war. And the result is we realized that we didn’t have quite enough to finish up—just because the small amount of work which had to be done after the war was going to be much more expensive than planned. And they went back to the Rockefeller Foundation and got, I think, two grants-— one of $250,000 and the other of $300,000—to finish it up. That fortunately proved just about enough to finish it. We were rather worru4 because, realizing that a project which represented as much new ground as this one did, you’re likely to need quite a lot of contingency funds because of unforeseen things; but fortunately we didn’t run into it. About the only thing was this rebuilding of the support system, which, if I remember right, cost only $l5,000—a rather negligible sum. But that was about the only unforeseen expense that we ran into. So we were fortunate in getting finished up as far as the major construction of the telescope and its auxiliaries.

Weiner:

But the salaries for the staff were separate, of course. They were paid from Carnegie Institution funds.

Bowen:

No. It was both, you see. The provision was that while Caltech would be responsible for the operating expenses of Palomar—that is, for the superintendent and the various janitors and lab assistants and what have you up there—and for upkeep, that each institution would hire what astronomers they could afford.

Weiner:

But I meant prior to that, the construction stage. In other words, you were director of the joint observatories, and no funds from the original $6,000,000 and the supplementary grants were used for your salary.

Bowen:

No.

Weiner:

That’s what I’m getting at, that the funds were largely used to contract for the work and for the actual cost of figuring the mirror and installing it.

Bowen:

That’s what they were given for. And, as I think I mentioned the other day, the gift was made with the understanding that the Institute would find, I think, $3,000,000 as endowment for operating expense.

Weiner:

Yes, I want to hear about how that was obtained.

Bowen:

This was, of course, in 1928 that this proposal was put up. Mr. Robinson, who was then president of the Southwest Bank, the largest bank in Los Angeles, was on the board of trustees. I believe he was chairman of the Caltech board of trustees. He was also a great friend of Dr. Hale and Dr. Millikan. And when this came up, he said, “Well, I’ll pick up the tab.” That was Henry M. Robinson. He provided then about $3,000,000 in securities which were turned over to the Institute. This, however, was in 1928 or ‘29, and most securities, particularly in companies, very rapidly deteriorated after that. A good many of them went bad completely, because they were equities. And although some of them now are coming back, I understand, the one thing that proved of value was that Mr. Robinson was somewhat of a sportsman and liked to shoot ducks; and he and a few of his friends had formed what is known as the Bolsa Chica Gun Club and had acquired a substantial amount of swamp land southeast of Los Angeles near the ocean. Fortunately, oil was discovered on that land, and that membership in that gun club is now bringing to the observatory something over $100,000 a year and we understand will continue to do for some time. And quite a lot of the operating expenses of Palomar Observatory have been paid from dividends from that fund.

Weiner:

Of course, he must have then made a supplemental gift of his share in this oil land.

Bowen:

I’m not sure of the details of just how it was given, whether it was turned over in his will or what not. I think probably it may very well have proven valuable before his death, and consequently he realized this was a real asset that could be turned over. I don’t know the details of that. Of course, it may actually have been set up as a company to handle it.

Weiner:

But as the telescope went into operation, you needed additional funds for special projects and for new instruments. What other outside sources of support were you able to get? And how were these obtained?

Bowen:

Well, of course, there were two problems: The Carnegie Institution and the California Institute of Technology. Dr. Bush, who in the early days was president of the Carnegie Institution, had also been head of OSRD. He was quite concerned about government interference with private institutions from his experience in OSRD; and consequently felt that it would be desirable for a few institutions, if they could possibly do it, to avoid accepting funds from the government—so that if later, because of this dependence on government funds, political pressures began to be exerted on institutions, there would be a few institutions that could speak up and say no because they were completely free of it. Caltech, on the other hand, has always accepted in rather large measure government funds and has actually run into these political pressures. n one or two instances, when Dr. Sturtevant was speaking out against the danger of atomic bomb contamination, one of his projects was immediately cancelled—also some of Dr. Pauling’s project were cancelled because of speaking out on political things. So there was some justification for this. However, as far as the Carnegie Institution, they were fortunate because rather early in the game they had shifted quite a lot of their funds over to equities; and consequently their income somewhat kept up with increasing costs. Also, they had been phasing out several of their departments. For instance, their archeology department was phased out shortly after the war; and their genetics department at Cold Spring Harbor has now been phased out and so on. And by a combination of having their funds in equities quite largely and also phasing out certain of their departments, they have been able to pretty substantially increase the funds available. In recent years they have been accepting some government funds, but limiting it pretty largely to capital expenditures, not to operating expenses. Caltech, on the other hand, has accepted a good deal of government funds, Also, there were some funds coming in. For instance, the Sky Survey was financed by the National Geographic Society. And there have been other sources of that kind for funds, Caltech has also had several quite successful endowment drives, which have increased their overall endowment quite markedly, and therefore enabled them to put more into astronomy.

Weiner:

There’s never been any separate attempts to raise funds for the observatories as such.

Bowen:

No.

Weiner:

It still comes from the two institutions.

Bowen:

Well, recently of course you’ve heard of this project for duplicating the 200-inch in the Southern Hemisphere—the so-called Carso project. There were attempts by the Carnegie Institution to raise the funds, which have not been successful as yet, however.

Weiner:

But still it would have been through the Carnegie Institution, The observatory has never been in any fund—raising position of its own.

Bowen:

No, Well, it should be realized that there is no legal entity such as the observatory. Its two parts are parts of the Carnegie Institution and the California institute, which are the only legal entities—— the Carnegie Institution and the California Institute. The observatory is not a legal entity.

Weiner:

So you’re two departments—a department of each of these institutions.

Bowen:

Yes, And consequently when it comes to business things, all checks are made out either by the Carnegie Institution or the California Institute and never by the observatory.

Weiner:

This must relieve the director of tremendous responsibility.

Bowen:

Well, he has to say who the check goes to and so on.

Weiner:

Yes, but it’s quite different from doing all the bookkeeping and fund-raising and worrying about where the budgets will come from each year. Have there been difficulties during your directorship in obtaining the funds that you felt were needed for an annual budget? Did you submit a budget every year?

Bowen:

Oh, yes. We submit a budget—two budgets, in fact, one to each institution—every year. We were almost never turned down. As a matter of fact, for a good many years the Carnegie Institution would ask for two budgets—one the minimum budget to operate and the other the desirable budget, in which we added several new things we wanted. And I think with only one possible exception, we always got the desirable one. Of course, I tried to be discreet in what I asked for.

Weiner:

Well, within those self-imposed constraints you got what you wanted pretty much.

Bowen:

Yes. I think the Carnegie budget during the 18 years that I was handling it a little more than doubled, and the Caltech one more than that because when we started out we practically had no budget. But the total budget of the observatory—that is, considering the fact that originally it was just the Carnegie budget-went up by something over a factor of four.

Weiner:

What range was it when you left, say, in ‘64?

Bowen:

It was a little less than a million, for both of them. It was roughly half and half.

Weiner:

For the two supporting institutions. And what about research grants? I noticed in the annual reports mention of at least…Well, not counting National Geographic, which was a specific project, Office of Naval Research is mentioned and National Science Foundation …

Bowen:

Those were both to Caltech. They were to men who were on the staff of Caltech. That is, half our staff received their salary checks from Caltech and half from Carnegie, as I mentioned before.

Weiner:

So they would be the principal investigators on the grant and their institutional affiliations for purposes of the grant would be California Institute of Technology with this as a sub—department perhaps of it.

Bowen:

This was a department of Caltech. As far as the institution goes, we were a department of Carnegie Institution and also a department of Cal tech.

Weiner:

That fills in the things I wanted to know about the funding. That relates to another question, and that is the educational aspects of the program. I ask it in two senses. One is that as you indicated almost 80% of the staff was getting near retirement age when you took over as director in 1946. You had the normal problem of replacement, and this was just replacement for the existing observatory—-for Mt. Wilson. And then you had the new problem for staffing the Palomar Observatory, but staffing it without any precedent. This is completely new equipment, auxiliary equipment; certainly a new style of doing astronomy in a sense. And so it was a question of not only finding people to take those spots and to replace the retired individuals, but also finding people properly trained or willing to be trained for this new function.

Bowen:

Well, of course, there are plenty of other observatories in the country where they have trained people. Greenstein was one of the first. He came from Yerkes, Several have come from Yerkes, Deutsch came from Harvard up here, I‘d have to go over the list to give anything like a complete list. And a few have been trained here. Going back to the educational thing, possibly should interpolate a little bit about that. The question came up originally as to whether the graduate school of astronomy or the department of astronomy from the educational standpoint should be part of the observatory. It was more or less left up to me to decide, and decided it would be better not to do so, because my office was up here where it wasn’t easy for graduate students to get to. My hands were pretty well filled in those early days anyway. And to have to learn a lot of the red tape of handling graduate students and granting degrees and all that sort of thing seemed to be rather out of line with my other duties, and it would be better to continue it down there. The other fact is that Caltech has always had the policy of having big divisions. That is, all the biological work is in one division, There isn’t a separate department of zoology, botany, embryology, and what have you. Also, between the wars there was a division of physics, mathematics and electrical engineering, which was all in one division under Millikan. At the end of the war, however, it seemed better, because they were revising the engineering department, to shift electrical engineering into an engineering department—one reason for it being that one of the top electrical engineers seemed to be the logical candidate for chairman of the division of engineering, namely Fred Lindvall. Also, after all, astronomy is quite largely applied physics; and in general, as far as training astronomers, think it’s usually realized the best thing for a youngster coming along is to essentially major in physics as an undergraduate and get a pretty thorough background of physics and mathematics as an undergraduate. Then when he goes into astronomy, he can really take it up from a quantitative standpoint rather than spending a lot of time on just a lot of qualitative things and then when he gets into graduate school have to take it all over again from a quantitative standpoint. So it was obvious that astronomy was very closely tied in with physics and mathematics, and it would be logical therefore to put it in the division of physics, mathematics and astronomy. So after quite a lot of due consideration (as I say, it happened on my recommendation), that was done. But, as mentioned once before, to properly correlate the graduate work with the research work in astronomy, it was considered that in general the head of the division of physics, mathematics and astronomy would be ex officio a member of the Observatory Committee. That meant that any of the problems involving the department or the observatory would be considered there, and therefore we would each of us be aware of what the other fellow was thinking about.

Weiner:

I notice the name of that division in the immediate post-war period was Division of Physics, Astro-Physics, Mathematics and Electrical Engineering.

Bowen:

There may have been a short period before the electrical engineering went out.

Weiner:

And astro-physics was included. Had Caltech ever given degrees in astronomy?

Bowen:

Yes, they’d given two—to Olin Wilson and Joe Johnson. But they had essentially taken the degree in physics but had done their research work up here at the observatory under somebody up here. There wasn’t any department of astronomy. It was essentially given by the department of physics.

Weiner:

Now, under this so-called physics division—using shorthand—astronomy is a separate department under the division, a degree-granting department. Not a department, a focus within the division.

Bowen:

Well, in recent years these departments have grown so enormously, particularly in graduate school, they have been appointing a sort of deputy chairman— think they call him executive officer. That is, for instance, in physics Carl Anderson is the chairman of the division. But then Green- stein is executive officer for astronomy, and there’s another executive officer for physics and another one for mathematics. But it all heads up in the chairman of the department, and he’s the one who usually signs the final papers and so on.

Weiner:

Now, how did this work out as a source of staff for the observatories— in other words, the new program there?

Bowen:

Well, of course, several of the men taking degrees there have stayed on in the staff.

Weiner:

Who were those?

Bowen:

Well, Allan Sandage is one.

Weiner:

He joined the staff in ‘52 then.

Bowen:

And Chip Arp is another one. I think there’s one or two over at Caltech. It’s always a little bit hard just offhand to remember all of the names, but two of the most outstanding ones are Arp and Sandage. Then another source has been this. The Carnegie Institution got funds from the Carnegie Corporation for a lot of postdoctoral fellows, and each year we have usually appointed maybe three to five postdoctoral fellows, who are somewhat like the old National Research Council fellows and so on, which are known as Carnegie fellows; and have brought in rather outstanding young astronomers. Usually they are appointed for one year, but it’s usually considered that unless they flop pretty badly they’ll get a second year of appointment. Those have been quite a source of new material. For instance, Maarten Schmidt was a Dutchman who came over on one of those. He’s the one who’s so much up on quasars and so on.

Weiner:

How about the National Research Council fellows? I’ve done a study on where they went over the period from 1919 on, and a large number of them went to Mt. Wilson. First of all, the majority went to Caltech. But I have found that many went to Mt. Wilson, and another group—the international Rockefeller fellows, a very large group of them from Europe—went to Mt. Wilson, What role did the NRC fellows or any other fellowships of this type, other than the Carnegie that you mentioned, play during the period of your association with the observatory?

Bowen:

Well, don’t think we’ve had very many of those since the war, There were a few, think, but they’ve been largely Carnegies, which we administer ourselves here, you see. That is, we were just told, “You can appoint so many fellows,” and we would get applications for them, and think we handled them much the same way the National Research Council fellows were handled. That seemed a fairly good procedure.

Weiner:

You had another category on the staff. You had a research associate in the annual reports. In other words, you have a regular staff listed and then you have Research Associate and then you have temporary Research Associate.

Bowen:

Well, first of all, the Carnegie fellows, like the National Research Council fellows, were largely limited to youngsters just out of a degree—that is, who didn’t have another job. Then the Research Associates: these were a Carnegie Institution appointment. They were largely for senior fellows—that is, for instance, when we got men like Stebbins out. He was head of the department and director of the observatory at Wisconsin. He’d be given the title of Research Associate. Also, we had the astronomer Royal out for a while—Sir Richard Woolley was out. He had spent, incidentally, two years here as a Commonwealth fellow in 1930, so he knew the place; and I happened to find out shortly after he took over as Astronomer Royal that he was very anxious to come here. He was of a primary theoretical background, but as director of the Greenwich Observatory, he realized he ought to know some observational astronomy. I found out he wanted to come here but was having difficulty getting dollars. This was not too long after the war, and so we gave him one of these research associateships for three months.

Weiner:

These were always temporary appointments.

Bowen:

Yes. Now, the other thing, which really was one of our biggest operations, were the guest investigators, if you’d like me to say a little bit about those. Of course, when we started operations out at Palomar, we realized that we were suddenly about doubling our observational capacity, if you wish, because we’d had the 60-inch and 100-inch up here, Now we were getting the 200-inch and the 48-inch down there, whereas we didn’t have funds to immediately double our staff. On the other hand, we’d be falling down on our job if we let this magnificent equipment just stand idle with astronomers around the country wanting to get at an observatory that didn’t have it. So after quite a lot of consideration we set up this guest investigator procedure. This was done on the basis—again there was a good deal of consideration given to this—that there should be no money interchanged either way. That is, in other words, we wouldn’t pay the man to come here. We would expect his own institution to continue his salary and pay any necessary traveling expenses or anything of that sort. On the other hand, we wouldn’t charge rent for the telescope, as some other observatories do—notably McDonald charges $100 a night for their telescope. We felt it was better not to charge the rent for it, because first of all the overhead on the 200-inch, even on the $6,000,000 capitalization, turns out to be $1000 a night—just interest and upkeep and so on. And the others would be up in the hundreds of dollars a night. Well, we felt that if you charged anything that was comparable to what it cost, then you would be cutting off a lot of your better observers. In general, we found it didn’t pay to come for less than 10 or 20 nights, because it always takes a little while to get used to a telescope. To come out for such a pro gram of 10 to 20 nights, most people would just have great difficulty in raising that kind of money; and you’d cut off often your better people, and you’d get just a few who had access to money, who often weren’t the people who used the telescope most effectively. So we decided not to charge. The other thing was that if you charged a purely nominal sum of maybe $50 a night, which they might be able to raise, then they’d feel they’d bought the telescope and could do whatever they wanted to with it, which may not be the wise thing. It was for those considerations that we said, “There will be no money interchanged either way. We won’t charge for the telescope, and also we won’t pay the man anything.” Then it was set out that anyone who wanted to come had to submit a program of what they proposed to do with the telescope in some detail, This enabled us to select between possible candidates for it, and do it on a much more objective basis than this man is good-looking and this man isn’t, so we’ll take the good-looking man. That is, it could be done on an objective basis, Oh, this sort of thing would happen. I remember one person wrote in wanting to use a 100-inch for a lot of stars around the Pole and didn’t realize that the 100-inch can’t be turned to the Pole. Or another thing would happen. A man would say, “I want to take a lot of spectra,” and would list the stars he wanted. On checking up, we’d find that half of those spectra were in our files already and had been taken for another purpose and could just as well be turned over to him. There was no use in taking any more telescope time on it. Well, those were just a few examples of why we found it very desirable to insist that they spell out in some detail what they were planning to do.

Weiner:

Who would review these proposals?

Bowen:

They went to the Observatory Committee.

Weiner:

Did you meet periodically on that?

Bowen:

Yes. Ordinarily what would happen: one of these applications would come in (they came to me, of course), then I would submit them first to the member of the staff who was most closely connected with the field that the man was proposing to work in and get his recommendation. Then with that recommendation, we would go to the Observatory Committee, who would then correlate all these together. I would usually have taken a look: “How much time have we got to give out this year? How many of these can we accept?” And then you’d sort of order them, take the ones that seemed to fit best with our program.

Weiner:

Ever keep any records as to percentages of applications received-number received, number approved?

Bowen:

No, I haven’t. The annual report, however, of course, doesn’t show those turned down.

Weiner:

It gives the names and the programs of those who did use it.

Bowen:

And the numbers, n general, we were running, as I remember it, a couple of dozen a year. Actually, I don’t think we turned down too many who had really suitable programs. There were some turned down, There’s no question about that, But most of them—it was because it just wasn’t a suitable program.

Weiner:

What were the criteria then for a suitable program? You mentioned one was not to use telescope time for something that already exists; another as a use of the telescope which was just not technically feasible because they didn’t understand the limitations of the instrument.

Bowen:

On occasion it just wasn’t a worthwhile program. It was a trivial thing and involved tying up a major telescope for a very trivial problem. But that wasn’t very often. It was largely these other factors—-that it just couldn’t be done with the telescope, or the plates were already available and so on.

Weiner:

I imagine, though, you’d have, occasionally, to assign some priority. You’d have a couple of good research programs proposed, and although, as you say, you took care of most of the people, you couldn’t always take care of them when they wanted to be taken care of; and you couldn’t guarantee to them that the seeing would be good.

Bowen:

Well, you normally expected to assign maybe 5O2 more time than the minimum required by the program just to allow for contingencies of that sort. We also rather, as say, insisted that a man turn in a fair— sized program. As I said, it wasn’t worth our while to train a man in the use of our instrument for just one night, and usually he tended to muff the first night anyway because he wasn’t familiar with things. So we usually insisted that it be a fairly major program of 10 or 15 nights at least, and we usually insisted that this be spread over maybe three months. For one thing, it’s always more efficient if you can have, say, a four-night run, get your plates, have maybe a month to study them, find out what wasn’t quite right about them, and then correct them for the next run. So we usually expected the people to be here for maybe three months on it. I know we had squabbles with a few of the people and had to turn them down, who found it was difficult to get away from their institution. But we took the attitude: “Well, we’re supplying you with a good many thousands of dollars worth of nights of telescope time. If your institution isn’t willing to give you a leave of absence to come and do it properly, we’re not interested. This is a joint operation between the two, and we should both contribute to it. We also said that any papers published should be published under the name of the man’s own institution, not our own. This was a little bit of a holdover, because of the fact in the early days, as you know, Hale founded the Astro-Physical Journal, and we had a contract with them when I took over bat all of our papers would go there that would be suitable for the Astro-Physical Journal, and that they would also more or less accept anything we sent in.

Weiner:

This was a little unusual, wasn’t it?

Bowen:

Which meant that we did the editing. Well, there were several other observatories that had similar contracts. That has now been dispensed with. But there was the problem—that we did not want to get into the question of editing these papers from other institutions, from members of the staff of other institutions, as you felt that you could run into all kinds of hard feelings and so on if you did that. So that was one reason for saying that we didn’t want to take any responsibility, either financial or editorially, for what they published on the basis of their work here. We simply said, “You should publish it under the name of your own institution, but simply with an acknowledgment that this was based on observations made at the Mt. Wilson-Palomar Observatory.”

Weiner:

n a sense you had for your own publications pre-refereeing. In other words, if they had agreed to accept all paper submitted, that means that you had the responsibility of serving as a referee. Do you recall whether at that time they had referees in general for their other papers that would be submitted?

Bowen:

Well, there were several institutions. Of course, the University of Chicago was of course published at the University of Chicago. I rather think that McDonald did the same. There were several institutions that had that arrangement; that the editing was done at the institution and that they would then accept anything that passed the institution’s referee—which meant that the papers were sent in not by the individual but by the institution.

Weiner:

Does that agreement still exist?

Bowen:

No, that we dispensed with.

Weiner:

What was the argument against it?

Bowen:

Oh, think that it was felt it was rather unfortunate to have the local refereeing. It’s always hard. For instance, when took over, Merrill was the editor. Seares had been the editor before him. Local editing always tends to get nasty in that when you send it into a journal and they do the editing, it goes out to a referee whom you don’t know. Here the referee is the editor who’s referring somebody in the next office, whom he’s got to eat lunch with that day. You get all kinds of personal implications and causes for internal hard feelings and so on. I think it was felt that we’d better dispense with it.

Weiner:

I want to return to the question of publications later. But I’d like to ask again about this question of priorities in terms of research programs. Given a good program with a limited amount of time and having two of these good programs competing for the same time, it seems to me you’d have to establish some kind of priorities, wonder how this was related to the current research needs as you interpreted them. In other words, both are not trivial but one seems more important at the time than the other. How did you make that kind of a decision?

Bowen:

Well, are you talking about guest investigators or staff now?

Weiner:

Guest investigators.

Bowen:

Well, that really went up to the Observatory Committee. They made the final decision on that.

Weiner:

I understand that they made the judgment on that, but what do you do when you get into a situation where there are two cases? Would you lean toward the thing that you felt to be of most current research interest?

Bowen:

Well, you’d have to make a judgment as to which is the most important for astronomy. The other question which you may want to go into is how we decided, particularly on the 200-inch, where there was very heavy pressure, for our own staff. There we set up a committee of three persons—as remember, it was originally Hubble and Merrill and then at the end it was Greenstein and myself and Sandage in ‘64. They changed from time to time. There was this small committee. Again we asked every staff member who wanted to use the 200-inch to submit a program.

Weiner:

You were saying that for your own staff you would ask them to submit a program in November.

Bowen:

Yes, Which would then come to this committee, which at the end was composed of Sandage, Greenstein and myself, Greenstein representing the spectroscopic people and Sandage the galactic and direct people. And we would ask them to send in how much time they wanted divided by quarters, because if you’re after certain objects, there are only certain quarters of the year when that’s up at nighttime. And they were to send in their request for time on the 200-inch and a brief discussion of what they planned to do and why it was important. This would then be passed around among the committee, and then we would each study it and make our own estimate of how much to allow. There was almost always quite a lot more than 365 nights asked for. Then we would get together and discuss it, compare notes, and make the final decision as to how many nights each one was to be assigned in each quarter. One thing that always surprised me was that when this was done with three different people—how closely we would agree. We would each bring in our list of how much time each man should be assigned. Then we’d compare them, was always surprised at how closely we would agree—in fact, how closely we would agree even though one of the men involved was a man on the committee.

Weiner:

That’s interesting.

Bowen:

He would turn in just about the same amounts that the other people did; so that there was usually very little disagreement. Then on the basis of this we would make up a list of how much should be assigned to each staff member who had requested time for each quarter. Then there were two men (one was Dr. Wilson for the spectroscopic run, and that’s a light-of-the-moon run; and Dr. Arp for the dark-of-the-moon run) who would take that and make detailed assignments. There are a lot of details there. Well, your man is assigned six nights this month. He’s got to worry about is there a bus up six nights apart. Should it be assigned in two runs or one run. You see, busses only go up twice a week, and also you don’t want a trip up on a Sunday or a holiday. There are various problems of that kind of just detailed things to be worked out. And they work it out on the basis of this. We usually normally assigned only 902 of the time as far as this written thing. That guaranteed the man would get that. Then the extra lO2 was used by the men to give them a little leeway. Sometimes you just couldn’t fit it into the trips up and down, and this way they could give the man an extra night, and he always felt happy about it if he got an extra night. Or some emergency would come up—some comet was in the sky that we hadn’t heard about, and somebody wanted a picture of it, or a super nova or something like that would break—and we’d, give a little leeway for that.

Weiner:

Did you find the ratio of staff use to visitor use changing over the years?

Bowen:

Not a great deal. Of course,, the staff use has come up, I think, some. That’s one reason why we’re getting still another telescope-— the new 60-inch. While the actual senior staff has remained about the same size (it was originally 15 or 16 staff members here at Mt. Wilson), the last year I was here and knew about the details it was something like eight and eight, which is the way it was planned to go; that Tech would hire eight, and we tapered off a little bit. That’s one reason we’ve been able to operate without more than doubling our budget. On the other hand, there has been quite an increase in the number of Carnegie fellows (there are three or four of those around) and NSF fellows (who are always avid young observers who want a lot of time), and, graduate students (Caltech has built up one of the large departments of astronomy), all of which need telescope time; and those, you see, have been added to the staff and probably take up almost as much as the permanent staff takes in toto, or at least half as much.

Weiner:

That cuts in then to the guest investigators?

Bowen:

So we have had to taper off the guest investigators somewhat. Which was contemplated, that would happen; and, of course, it is not too bad in that the Lick has, got their 120-inch; Kitt Peak is coming in with big telescopes that are available to people in, general, and McDonald is getting a new one, and Hawaii is getting a new one, and so on. So we were able to fill a real need there when there was this big expansion in astronomy but very little time taken to build these things. In the ‘SOs and ‘60s there just wasn’t an additional telescope available.

Weiner:

Do you have any feeling for the ratio as it existed during these years of staff time to guest investigator time? This is the 200-inch I’m referring to now.

Bowen:

Well, the 200-inch in the early days was not used too much by the guest investigators. They were largely 60 and 100. There was a great deal of 100-inch time used then. There were always a few. For instance, Whitford and Stebbins went up there and Keenan has gone up there. Quite a few of them have. But, you see, if you look back, in 1950 ‘the only big telescopes in the country were our two, 60-inch and 100-inch and the 82-inch at McDonald and the Victoria 72-inch. They were about the only ones in the country. The staff of Victoria and the staff of McDonald had their own telescope to use, and there were practically no other astronomers who’d had experience with large telescopes. Well, it was a little bit unwise and probably not the best use of telescope time to throw a man directly on the 200-inch. After all, that was a very unique instrument. The people who had had experience using big telescopes were our own staff. Now, that has gradually changed; and as people have gotten a few years work on the 100-inch, we would then occasionally invite them to go down there. Keenan has gone down there quite a little, Whitford, who had worked with the 100-inch quite a little, went down there. But know people wondered why more people weren’t put on the 200-inch, but there were very good reasons for it. There were very few people except our own staff who had had experience with large telescopes, and you don’t start them out on the biggest one.

Weiner:

We’re resuming now after a break for lunch and a tour of the optical shop and plate archive (the plate vault). As we left off, we had been discussing the guest investigators, how the judgments were made and how they fit into the total program of the observatories, I want to ask next about the changes in research emphasis over the years. Originally the time was divided. I don’t know if it was evenly divided, but part of the time was apportioned for the 200-inch for direct photographs and then part of the time for the spectrograph. I want to know if that ratio of time changed very much during the following years.

Bowen:

Unfortunately the moon sees to that. You can’t do direct photography or critical photoelectric work when the moon is out, and the moon is out about half the time. Consequently, that pretty well sees to it that you have to spend half your time on spectroscopic work and the other half on direct photography, photoelectric work. Of course, we tended to shade it a little bit in favor of the direct photography. That meant going over in the nights that were less than quite half free of the moon, because of the fact that at Mt. Wilson these same things—direct photography and so on—are hampered by the lights of Los Angeles. And consequently even under the best conditions of no moon, it’s been increasingly difficult to do critical work because the sky there, depending a little on the direction, is from two to five times as bright as the sky at Palomar. Consequently all of our critical direct work had to be done at Palomar. And on that account we right from the beginning tended to favor that a little bit. But on the other hand, you can’t change much just because of the moonlight.

Weiner:

What about emphasis of research subjects within these other divisions? Do you recall trends?

Bowen:

Well, of course, when the 200-inch started, one of the biggest projects was the reinvestigation of what we might call the scale of the universe—first determining the distance of Andromeda and then some stepping out to more distant things, which included such things as extending the red shift measurements out to greater distances and everything of that sort. One of the big factors, as was mentioned this morning, in this was the necessity of making precise determinations of magnitude, and the realization, which came at about that time, that the old photographic magnitudes were pretty inaccurate, plus the development of new photomultiplier schemes for making very precise determinations. So that one of the, big things that developed and occupied more and more time on the telescope was photoelectric measurements, both for determining this basic scale of things but also for stellar evolution—determining the H-R diagrams, if you wish, as they depend on red and blue magnitudes and so on. So there was somewhat of a shift away from direct photography to photoelectric measurements of things. Also, in the spectroscopic things there was this thing that I’ve mentioned earlier of going to fainter stars, particularly getting the spectrum of Population II stars, most of which are pretty faint, because the characteristic ones are in globular clusters. In general, however, the main emphasis has been going from qualitative intensity measurements to quantitative intensity measurements. This has gone over into the field of spectroscopy where instead of using photographic procedures they’ve been using photoelectric scanning procedures; and also in the straight photometric things. Of course, the original photometric development was first just the measurement of one magnitude. Then, as I mentioned earlier, there was the emphasis on the relative magnitude in blue light and red light and possibly in ultraviolet light. And then as things developed further, people got interested in even more detailed division of the spectrum and measuring intensities, until within the last few years we have such things as Oke’s multi—channel spectrometer or photometer, which consists essentially of a grating spectrograph which spreads the spectrum out into a spectrum several inches long, and then located along that are up to 33 or 36 photo-multiplier tubes which simultaneously measure the intensity of the light in narrow and sharply defined bands of the spectrum. This was done first using a scanner, in which you simply used a spectrograph with a grating which could be turned, and you projected first one region of the spectrum, then another and another and another onto the photomultiplier tube. But this, of course, was very wasteful of valuable telescope time because of the fact that you were only measuring one at a time. With this new thing you measure up to 30 or 40 simultaneously, and therefore speed things up very greatly as well as eliminate uncertainties due to changes in the transparency of the sky and things of that sort. So that that is again a very much coming thing: these multi-channel things. Of course, another thing which has developed and is particularly important for this spectrum of exceedingly faint sources such as are needed for the red shift of very distant objects, galaxies, quasars, what have you, are things like the development of the image-intensifier tube, in which instead of throwing a spectrum directly on a photographic plate, one projects it onto a cathode of some size——in our case an inch and a half across—; the electrons are then speeded up and refocused on a phosphor, using a magnetic field. Then, since they are speeded up with several thousand volts, the phosphor is much brighter than the original light. Actually as we now do it, there are two stages in this so that the final image is some thousands of times brighter; and then in spite of losses, we are able to take photographs of the spectrum of a galaxy that used to take many hours now, in maybe 15 minutes—the gain is a factor of 10 to 20—which avoids these tremendously long exposures that Humason used to have to take in getting the spectrum of very distant galaxies.

Weiner:

These new developments in the auxiliary equipment are frequent. I’m curious about the source of them—whether they come from the staff (these new innovations), whether they’re things that have been developed elsewhere and which seemed to be suitable for what you are doing here.

Bowen:

Well, the first one of these—the multi-channel thing—was a rather obvious, straightforward thing, because it was just a matter of dividing up the spectrum and instead of one photo-multiplier tube, putting in 30 or 40. That was developed here by Dr. Oke. The image-intensifier tube has quite a history. It was realized shortly after the war that the photon efficiency of a photoelectric surface was substantially greater than that of a photographic plate. In general, with even our fastest photographic plates, it takes about a hundred photons to produce one grain. Whereas, with a photoelectric cathode, we get one electron off for every five or ten photons impinging on the cathode. And since your ultimate limit depends on the statistics of photons coming in, that meant that you had 10 to 20 times the efficiency using photoelectric means. We had quite a discussion of this back 15 or 18 years ago between Dr. Baum and myself, and then one time when Dr. Bush was out here we discussed it at some length with Dr. Bush. Obviously this was a major development, to build up tubes in which these electrons were focused on phosphors. There was development of phosphors, development of the proper vacuum tubes and so on—a type of development that was rather beyond what an observatory could tackle. Fortunately, a somewhat parallel development was being made by the military, first for their snooperscopes for seeing with the infrared and then more recently for work in seeing at night, amplifying what a soldier can see—someone sneaking up on him or so on. On the basis of this discussion, Dr. Bush got in touch with Merle Tuve, who was quite an electronics expert, and furthermore knew his way around the large companies that were developing this sort of thing. Dr. Tuve had been head of the proximity fuse project during the war; and since that was done quite largely through commercial companies, he was thoroughly familiar with the facilities that various commercial companies had and with the men, because you don’t just write to a company and ask them to develop something—you get in touch with some of their key men that are knowledgeable in the field and get them interested in it. Well, as a basis of this discussion, a committee, known as the Image Tube Committee, was set up, which Merle Tuve was chairman of; our Bill Baum was on the committee; John Hall, who was then at the Naval ‘Observatory, is now director of Lowell Observatory; and Dr. Merton from the Bureau of Standards. They, working largely through RCA and Westinghouse, got them interested in developing this, using funds from NSF. This was finally developed, and the first models came out some three or four years ago—I guess a little more than that, possibly five or six years ago. Unfortunately, it posed some rather serious problems for us, because we had based our very fast spectographs on the Schmidt camera. Unfortunately, the Schmidt camera forms its image in the center of the incoming beam, which was all right with plates half an inch by one inch, which did not intercept too much of the light from, say, a three inch beam. These new tubes, however, were themselves four inches or so in diameter. They had to have magnets around them and shields and so on, which built up to a diameter of six or eight inches and obviously would completely obstruct the incoming beams. So it meant developing new optics of comparable speed—that is, of focal ratios less than one—with critical definition; and that somewhat held up the project. The other thing was that with this so-called Carnegie tube which came out of this committee’s work, the images formed on a phosphor would then have to be reimaged on the plate—and again it had to be a very fast lens of focal ratio one and a half or less. To build up an optical system that would reimage at that speed without losing definition was again a new problem which had to be solved. So there was quite a little delay in getting it into action. But the spectograph was completed about two years ago and has been in use for the past two years and producing spectrum at a rate of usually several an hour instead of one or two a night, and has quite changed the picture as far as study of quasars and things of that sort. In fact, it’s rather amusing: the original one was designed to use plates, but these plates—due to the fact that the image is formed in the center of the beam—have to have a rather complicated plate-holder and it only holds one plate. And we’re finding that the time taken to change plates and develop them between runs and so on is taking more time than taking the pictures, which is very inefficient. So a new reimaging camera of quite a different type has been designed which will permit the use of film, so that we can change the film very rapidly, load in enough for a night’s run, and we hope it will very greatly speed up taking these things. This is in the process of construction now and should be in operation in another six months.

Weiner:

You mentioned in the development of the image tube the advantage that Merle Tuve had because of his familiarity with industry.

Bowen:

I possibly should say a little bit more about this development of image tubes. The first development was in France by a Dr. Lallemande in Paris. In his case he actually put the photographic plate in the vacuum, and the image was recorded electrically by the electrical effect of the electrons striking a photographic plate. This, while producing very fine results, was not too practical because of the necessity of breaking the vacuum and essentially starting with a new vacuum tube every night and also the fact that you didn’t know until the night’s run was done whether you had things properly adjusted or not, Another development was in England by McGee at the University of London, In his the electrons were speeded up and came out into the air through a very thin mica window, which again, though it worked very satisfactorily, was very delicate, because these windows were only about four microns thick and there was always danger of breaking one.

Weiner:

I notice the reports of the Image Tube Committee were published as part of the Carnegie Institution’s yearbook right after the Mt. Wilson reports, so there’s some record of their work—although they’re very brief reports, usually a page or two. But was interested in the role of industry, not only in this development but in others. It seems to me that you were developing needs for unprecedented kinds of optics applications. Some of the things were being worked out here. It’s sort of a two-part question that I have to ask. One is: were there subsequent applications of optical auxiliary equipment that were developed in connection with the observatories here—applications in industry or extensions of these things or refinements of it? And the second part of that is: was industry in any position to really provide the kind of technical help needed in the early days of the development of the 200-inch when you were developing the auxiliary equipment?

Bowen:

Not too much as far as the auxiliary equipment goes. Of course, on this question of vacuum tubes, vacuum things, there are very special techniques and often trade secret sorts of things. How did you get something that you seal off that the vacuum will remain high? How do you make these various very sensitive cathodes? Things like that, which are more or less trade secrets, and it’s very difficult for one or two men working alone in an observatory to break in. Usually, there it is easier to get industry to do things for you than it is to try to do it yourself. As far as the optics goes, it’s been a little the other way. The standards as to definition required for astronomical work is of a different order of magnitude than what usually goes for most commercial applications. For instance, take this question of cameras for use with this image tube. I recently received a reprint from Germany, an article written by one of the top German optical designers, in which he gave the designs of several cameras for use with image tubes, and he gave the so-called spot diagrams which show the spread of the image of a point source as produced by his lenses, In the area of a lens to which it was to be used, there were areas in which the light was spread over an area of 150 microns, which from our standpoint is completely intolerable, in our designs for these optics to be used with the image tubes, we have felt that we had got to hold the images in general to 10 microns and never to go over 20 microns. That has meant we often have had to limit things somewhat, but we have also been able to hold them to those very much tighter tolerances. On the other hand, since these optics are made in our own shops, we don’t shy away from aspheric surfaces, which are not too feasible to make commercially because there has to be a lot of handwork that in making things for commercial things these days would be prohibitively expensive. So that in general we’ve had to depend on our own construction and design for a great many of our things. In fact, as I mentioned in the Hale talk, at the present time I think a good deal of the most sophisticated optics is now in the astronomical observatories rather than in the physics laboratories.

Weiner:

What about subsequent applications of optics that had been developed in astronomical observatories?

Bowen:

Well, the Schmidt camera has been used some commercially but not a great deal—I think largely because the commercial companies shy away from any of these aspherics, and the Schmidt camera requires a fairly steep aspheric. That’s the reason I think they’ve shied away from it. But we feel we can do it since we do our own work, it costs money, but it’s the only way we can get the results we want. The trouble is: if you allow the image to spread this way, you begin to get spurious results. You measure the shape of a line or something like that, and if part of the shape is due to errors in your lens, you simply get the wrong answer; and it’s often very difficult to take it out.

Weiner:

It seems to me that in the post-war period you see the development of firms specializing in astronomical and optical equipment of a more scientific nature, I think of Perkin-Elmer for one. Do you know anything of how this came about—whether in fact they were responding to what they felt would be a need in terms of some boom in astronomy?

Bowen:

Well, the only one that I am very familiar with is the Boiler and Chivens firm here in South Pasadena. Boiler and Chivens were two young engineers who took their degrees at Caltech. I happened to work with Mr. Chivens quite a lot during the war, as he helped in the design of some of these special cameras that we were using for our war work. They started a small firm and soon got in quite largely into building astronomical telescopes. They’ve done a good deal of the auxiliary equipment for the Kitt Peak Observatory, the 88-inch for the University of Hawaii, and several other things. They were a small firm, had limited capital. Mr. Perkins found out about it. They were doing a magnificent job. They really took time to do a very careful job, and their work was always considered of really astronomical caliber. And so Mr. Perkins took them over. Mr. Perkins told me once he didn’t care whether they made any money or not. He was just interested in doing it somewhat as a contribution to astronomy, because by taking them in he could provide the capital that they needed to handle these big jobs. They were so small a company that getting a million dollar job, as some of these things were, and not being paid immediately would sort of put them in the red.

Weiner:

By that time he had been pretty well established.

Bowen:

I didn’t know much about his early history.

Weiner:

Did you have much personal interaction with him?

Bowen:

Well, not too much until the last eight or ten years. He has always, as you know, been interested in astronomy. Usually when he’s out in this country he used to drop in and see me for a few minutes, and we’d often go out to lunch together; and I’ve seen him casually that way probably a half a dozen or a dozen times. That’s been my main contact with him. And occasionally I’ve advised him a little bit on some of the Boller and Chivens problems, as I’ve worked along with Boller and Chivens some—I’ve advised them on just a voluntary basis. I might say that I’ve always felt it was very desirable to encourage outfits like Boller and Chivens and another optical firm here—Davidson’s— because when I first took over up here we were developing a lot of new equipment. I think we were about the first observatory to really exploit the Schmidt camera, for instance—at least in this country—and particularly to exploit it for spectrographs. We were under a great deal of pressure from other observatories who wanted to duplicate this equipment. There was no commercial firm available to make it, and they came to us: “Can you make us a spectrograph?” “Can you make us a camera of this kind or the other?” Well, it rather put us on the spot. They were first—class observatories; we would like to help them out. On the other hand, we’re a nonprofit tax-free organization; and if we start doing commercial work, we’d seriously jeopardize our position—that is, if we do it to any appreciable extent anyway. It very much put us on the spot. So at that time I know we encouraged and even helped some of these firms, such as Boller and Chivens, and Davidson, to keep them going—feeling that if we could get them going and they did a good job, then it relieved any pressure on us. We could just say, “Well, here’s a good place to get your stuff. Go to them. Don’t come to us for it. They’re in a position to do it, and we can’t.” So we’ve taken that attitude. In fact, right now I personally designed a spectrograph for Boller and Chivens—didn’t charge them anything. It was just for fun—just because I felt that it was worthwhile seeing that they did a good job and also that they kept going; that they didn’t lose out on the things.

Weiner:

Are there many companies like this?

Bowen:

Not too many. The trouble is that with astronomical work in particular, the precision required is of a different order of magnitude, as was mentioning earlier, than is required for most commercial things. It’s true that some commercial things are now getting to require that precision, so it isn’t quite the problem that it was before the war. I remember one case before the war. We wanted some precision ways made for a big Rowland spectrograph over at Caltech, It was too big to make in our own shop. We went to a local shop that had a pretty good reputation. We specified that these ways should be straight and parallel, to a thousandth of an inch, When they came they were out by a sixteenth. Apparently this company just didn’t know what that kind of precision was, how to obtain it; and we had to go in and redo the thing ourselves because they just weren’t used to that kind of accuracy for commercial work, and they just had no appreciation of what it meant to get that kind of accuracy.

Weiner:

In the immediate post-war period, people were doing ten thousandths.

Bowen:

Well, we are too, so far as that goes. But so many of the commercial things don’t require it, and there aren’t too many companies that have the feeling for it—what’s required.

Weiner:

Is this true also in Europe? Had there been any firms specializing in astronomical instrumentation that have developed either in Japan or in Germany or elsewhere?

Bowen:

Well, of course, there was before the war. There was the old Zeiss and several companies that were making laboratory instruments that I presume would have done somewhat better. But in this country there were very few that did, And that’s, as I say, why we felt it was very desirable to encourage groups like the Boller and Chivens group, who apparently have learned it and are able to do it now.

Weiner:

Well, that answers the question. Another thing related to this is the fact that since you had to do it yourself, you developed a pretty skilled group—I think of Bruce Rule and others who think can be compared to the accelerator builders in nuclear physics, a group of skilled people whose knowledge is really transferrable and is very much in demand, It might be good to say a few things about how this special competence developed, taking Bruce Rule for an example, if you think that is a good way of approaching it.

Bowen:

Well, think probably it’s developed by a man like Bruce Rule, who came in as a young student fairly fresh out of his engineering training (I think his basic training was in electrical engineering, although he had a fairly sound background in mechanical engineering), and working on a project such as the 200-inch, which he did for a good many years, under such people as Anderson, who was a scientist (Anderson had built ruling engines, which is probably one of the most precise jobs we have to face), and who had a real appreciation for that sort of thing and just developing a feeling for it. On the other hand, they are so scarce that, for instance, Rule, who is probably the outstanding engineer in that field today, has been asked to serve as consultant on practically every major telescope project anywhere in the world. And he’s been consultant with ESO, with English projects, with Canadian projects, with Kitt Peak, and the Lick telescope. Practically all of those have come to him for a lot of detailed help on things.

Weiner:

But he is permanently on the staff here.

Bowen:

Yes, he’s permanently on our staff; and he’s so valuable that he’s now considered a staff member of the observatory along with the astronomers.

Weiner:

That raises another question about the different groups working at the observatory. I notice in the annual reports you refer to a research division, and then this was divided at one time anyway into solar physics as one group, stellar motions and distances as another, stellar photometry; another group is stellar spectroscopy; then nebular photography; and then the physical lab and editorial division. Now, is this designation just a convenient way of describing what is going on, or does it actually have some organizational meaning?

Bowen:

Well, there was some organizational meaning. This was the organization when I took over in ‘46. For instance, Hubble was the head of the nebular division; first Adams had been, and then on his retirement Merrill was head of the spectroscopic division; Nicholson was head of the solar division; and so on. And I found it in the early days very convenient, because if a problem came up involving, for instance, direct photography, I would go to Hubble and discuss it with him. Having gotten his answer, that was it. Or if it was spectroscopy, I would discuss it with Merrill. However, there were some problems that developed as these men dropped out. You see, Hubble dropped out in ‘53; Merrill, I think, in ‘52; and Nicholson in ‘56. There were some problems involved as to just who should replace them; and also I felt that it was a rather unwise set-up to be compartmentalized this way with the younger people coming on. In the early days it was all right when we had these older astronomers here who had been here most of their lives, had pretty well gotten into a groove, if you wish, in the sense that they had discovered what field of astronomy they wanted to work on and presumably would spend the rest of their lives in that field. However, with a lot of young people coming in, often they weren’t quite decided how they wanted to work; and as long as it was compartmentalized, there was a tendency to bring a young fellow in, and he would, say, be interested in spectroscopy; so he would be assigned to the spectroscopy department. Then, however, if he got an Idea that he wanted to take some direct photographs, well, that was crossing the division lines. •He had to go to the head of the other division and get it straightened out with him, and occasionally this would cause a certain amount of raising of eyebrows and so on. And it didn’t seem wise, because you wanted these young fellows to be pretty free to dive into any field that they found of Interest or had some Idea that they wanted to follow down. So as these people retired, we just quietly forgot about appointing any successor. The divisions were finally just left out of the catalogue or of the list of staff. We just considered them as one staff. It seemed that with the situation of the older people, they were pretty well frozen in their field, and this question of crossover didn’t come up. But starting with an entirely new staff of youngsters, it seemed desirable that we didn’t have those sharp divisions that were difficult to cross over. Another factor was, of course, that after the war, with a lot of these new techniques coming, such as the photoelectric technique and now the computer techniques and so on, a lot of new fields were developing, a lot of new ways of doing things. There was often the question of which one of these fields should you go in? Now, I think, if it was necessary to divide up into divisions, you might very well find there was quite a different set of divisions than was appropriate to the programs of 1950. That is, in 1970 you might very well divide up in quite a different way.

Weiner:

You might have one called quasars, for example.

Bowen:

Yes.

Weiner:

Do you think this sort of faded out about the mid ‘5Os?

Bowen:

Yes. It was more or less that as these people retired, they just weren’t replaced. And it happened that Hubble died in ‘53; I think Merrill went out in ‘52; Nicholson I think was ‘56. It just happened that they all went out within a few years of each other. So when they were gone, we just forgot about it.

Weiner:

Another question relating to the division of labor at the observatory was the role of theoreticians. Did they occupy a special place? Now I refer here to staff, but also I’d like you to extend it to the research associates or the guest investigators.

Bowen:

Well, we had a certain amount. On the other hand, our feeling here was that here we had, particularly during the ‘5Os, the most magnificent set of observational equipment in the world; we don’t have funds enough to really fully staff it; it’s much better for us to more or less concentrate on the observational side of things and let the people back east and in Europe, where they don’t have the skies for doing good observational work, do the theory. This is no way meant to say that we didn’t appreciate the value of theory. But it Just wasn’t the most strategic thing for us to do here at the Mt. Wilson—Palomar observatory. We did try in building up our staff, particularly at Caltech, to pick observational astronomers who were unusually strong on the theoretical side, such as Jesse Greenstein, Guido Munch, and so on, who while they were primarily interested in observational astronomy, had spent enough time in theory so that they could read intelligently the theoretical literature and apply it to their problems. We did try to go that far, in trying to get people who had for an observational astronomer a rather unusually strong background in theory. But we didn’t feel that it was the strategic thing for us to build up a strong theoretical department here in theoretical astronomy because of the fact, as I say, of somewhat limited resources and the fact that we had a pretty unique set of opportunities for the observational side.

Weiner:

Yet in your annual reports there was very often—I guess in every one—there was at least a small section on theoretical work.

Bowen:

Well, some of these people in connection with their observational work would do theoretical work, or they’d apply theoretical work that had been done somewhere else to their work here. So, as I say, it wasn’t at all a failure to appreciate the value of theoretical work. It was simply that we had the inside track on observational things, and we’d better concentrate on that rather than trying to compete with the people in the east who didn’t have it.

Weiner:

This would also mean that you’d have relatively few fellows and research associates who were primarily interested in theoretical…

Bowen:

Well, we would often bring in a theoretical person particularly as a research associate. Of course, they didn’t usually come here. Well, once in a while a guest investigator would come just because he wanted to get at observational material or discuss things with observational astronomers.

Weiner:

Who, for example, do you recall?

Bowen:

Well, Oort is one.

Weiner:

That’s interesting to me. I was thinking about the concept of team research. Maybe the term is wrong, because I guess make an assumption that just because you have so many people at one place, that it necessarily is team research. I was thinking that perhaps this is a wrong idea. When you were describing each one’s individual program and that in fact the man can work as an individual—that he sets up a program which is approved and then goes to work on it—have you found over the years a clustering of people on a specific problem working in some way as a team?

Bowen:

Not too much. After all, your observing is a one-man program. There’s only place for one man up in the cage. And while there’s certainly been no objection to men teaming up—and occasionally you will find some joint articles that follow from that——in general I think that people have had their own ideas and tended to work on their own programs. The main cases where there seem indications for something of this would be something such as in the early days when some of the older people were working on programs, it was very desirable (for instance, this scale universe program) to get some accurate photometry. But for an older man like Baade or Hubble it would be foolish to go back and try to learn a lot of electronics. They might team up with somebody like Baum, who would get the photoelectric measurements for them, which they might use then to calibrate their plates and things of that sort. There were some cases of that kind but not too many, say two techniques would be involved, and two men would team up, each supplying his own technique. But in general there wasn’t too much of that. There were some. If you look over our bibliography, there are some cases where there are joint articles between various groups. I don’t know of any cases where there was a long-range team-up. It would be for some specific program where two or three people—one person could supply one part and another person another part—would team up and put their stuff together, but not in terms of a long—period cooperation, a long-range program.

Weiner:

Even in the individual work, I guess it would be pretty much of a solo thing—not only the observing, but actually processing the plates and measuring them. Was this done by the observer?

Bowen:

Some of it is. We also have quite a group of so—called research assistants, who are men or women usually with a bachelor’s degree in physics or something of that sort. If there are spectroscopic plates, they have to be measured up; and often measuring a plate may take several days. And they will often be turned over to one of these people who have a scientific background but yet not enough to go on programs of their own but yet can save the time of an astronomer. So that’s done quite a little, We have I guess nearly a half a dozen research assistants up here and a similar number at Tech.

Weiner:

But they are assistants…

Bowen:

Usually their name doesn’t appear on the article.

Weiner:

They’re assistants in the same sense that people in the accelerator laboratories are. They have scanners who are looking over the results and so forth.

Bowen:

Once in a while a case comes up where an assistant does rise to the occasion. We had, for instance, Miss Swope, who was originally hired as Baade’s research assistant. We realized she was better-trained than most of our research assistants were, and she worked with Baade for quite a few years. She came—don’t know—about 1950, worked with Baade for six or eight years, thoroughly learned his techniques Then Baade suddenly died. He was a very avid observer, and we were all quite concerned, because he had probably five years of material that the observations were made and never assessed. Well, Miss Swope rose to the occasion and did it and published the articles, using her name and Baade’s name. In a case like that she did the whole thing—it’s true, using techniques that he had taught her—but she had enough background; she could also somewhat make the interpretations. And when this happened, we advanced her to research fellow, because she was then essentially on her own, But that doesn’t happen very often ,,, Of course you know Humason’s story.

Weiner:

Yes, starting out as the janitor…

Bowen:

And moving on up to full astronomer.

Weiner:

How did he function? What role did he play during the development of the 200-inch and the use of it?

Bowen:

He helped quite a lot on the site survey. You see, for the original site survey they had a dozen 4-inch telescopes which were distributed all over Arizona and the southern half of California. And since this was a question of observing every night, they hired largely local high school students and people like that to do it. But obviously these need calibration And he did a good deal of going around and spending a night or two with this man and a night or two with the next, letting this man observe and then he would check it and so on, and getting calibrations on things. He did quite a lot of that sort of thing. He was a magnificent observer. On the other hand, when it came to theoretical interpretations, he was pretty well lost, of course. And one of the main things he did was getting these spectra of very faint objects where it was a question of sitting there night after night on one little tiny spectrogram like this, and he was very skillful at guiding a telescope and generally taking care of things like that.

Weiner:

When did he die?

Bowen:

Oh, he’s still alive.

Weiner:

Oh, yes, remember. Helen Wright had told me.

Bowen:

I had a letter from his wife just the other day. He’s living up north of San Francisco.

Weiner:

I’d like to ask now about the development of radio astronomy in terms of the optical identification work that started to be done here by Minkowski—and who worked with Minkowski on it?

Bowen:

Well, Baade did a little.

Weiner:

I guess those were the first two. It seems to me that this was a very special role that developed for the 200-inch in the ‘50s, one that was unanticipated.

Bowen:

Well, there was quite a story about that. Of course, radio astronomy developed right after the war. This is possibly a little bit of an aside. There was quite a lot of discussions between myself, Dr. Bush and Dr. DuBridge about it. You see, the early development came in England. Well, some of the very early was in this country, but the real exploitation of it came in England and Australia—in Australia, it was by Taffy Bowen. And Bush felt rather strongly that just because we had a lot of money in this country we shouldn’t go out and raid them of their good men but should help them to develop, and he really believed it to the extent that he went to the Carnegie Institution, of which he was a trustee, and got them to give quite a sum to Taffy Bowen to build a big one over there, which was then supplemented by government there. On the other hand, DuBridge, who, as you know, was head of the big radar project at MIT during the war, so was very familiar with these developments, wanted to get something going here, I was asked did we want it in the observatory. I said, “Well, I think not, because, after all, from the very nature of the things, these are not going to be located at our sites. They want to be down in the valley, whereas we need to be on the mountain top.” That is, they need to be in a valley where they are shielded from interference from other short-wave radios. And so they went up into Owens Valley, which is a very sharp valley 2- or 300 miles north of here, And I decided I had enough sites to look after and not a couple more, particularly with techniques with which I wasn’t at all familiar and so on. So it was set up I think more or less under the physics department, although that again was the physics and astronomy division. Actually the first one was set up on Palomar. There was a little delay in locating their site up in Owens Valley. They were originally talking about one up north of Ventura, which for some reason they couldn’t get title to, and so they decided to go up to Owens Valley with it, And in order to get something going—Bolton was here then—they set up a 25-foot dish on Palomar, which meant a little overlapping with us, but it was known to be just a temporary thing until they could get a permanent site, Then once they got up there and began to get results Their offices are in Robinson Hall, where they’re right next door to the astronomers. There was a good deal of give and take between them, and with Minkowski, who was much interested in the thing. And so that cooperation developed right away, and they have right along worked back and forth between the two groups. Of course, a lot of Minkowski’s work was from these Cambridge catalogues which were not local—that is, the surveys were made by the Cambridge group—the C-1, C—2, C-3 group catalogues.

Weiner:

We were talking about the radio astronomy work and the relationship to the work going on in Cambridge and elsewhere.

Bowen:

Of course, one reason why our people participated quite heavily in that was the sky survey, which of course went to very much fainter objects than any other survey of the whole sky. Minkowski, of course, was in general charge of that sky survey; and consequently it was very natural, as these reports of radio sources, and particularly as their locations became more accurate, to start looking them up on the sky survey. And since a lot of these things were coming out while the sky survey was in progress, a good many of these prints had been distributed generally; so the only place that they could be looked at was here. This is a little digression now. He was the one who approved each plate for the sky survey. That is, I think we took nearly twice as many plates as there were fields, simply because there would be a little defect somewhere or the exposure wouldn’t be right or the seeing wasn’t quite right. And in doing this, Minkowski made a point of going over every plate with a hand magnifier and checking to see that the plates were all right. Well, very naturally in the course of that he was picking up all kinds of unusual objects, because in going over it with a magnifier, you’d see an unusual object. So he was a very natural person to then take over this question of looking for radio sources. That is, here is a radio source reported in this region. Often the early reports were quite inaccurate, but with the sky survey available before him, often with better plates than were available to other people because we had the original negatives here, he could then check: what is the likely object to be this radio source. Of course, in the first cases, they didn’t know what to look for. They didn’t know what type of object were the radio sources. But he gradually built up a feeling for that sort of thing, and so was in a better position than anybody else to continue in that field.

Weiner:

And he’d do it. Once he’d identified a likely source, then he’d observe. He’d ask for time …

Bowen:

And then he’d often take a look at it with the 200-inch to get a more detailed picture.

Weiner:

And very often this in fact identified it.

Bowen:

Yes.

Weiner:

Now, that has grown, of course, with the growth of radio astronomy, so that this was almost a fulltime occupation of many of the people on the staff.

Bowen:

Well, yes and no. Of course, one thing which has had the opposite effect is that in those early days, often the position of the radio source would be uncertain by many minutes. That is, they were using small dishes with a wide cone and they could only locate it within quite a few minutes, and there’d be a large number of objects present. Now with their later techniques, they have narrowed that down to probably uncertainties of a second or two. Well, then there are often just no ambiguities. There’s only one object within the probable error. And the other factor is they’ve gotten to know what sort of things to look for, which they didn’t know before: “Well, is it a nebula we look for? Is it a star or what is it?” So that there’s been that opposite effect— that now it takes a much shorter time, because you just go and locate that point on the print. And it’s there or it isn’t there.

Weiner:

Then there’s no need for further optical work really.

Bowen:

Well, except that often you do then want to get a better look at it—probably not from an identification standpoint but Just to understand what the radio source is. So there have been those opposite effects; also the fact that a great many of those things have now been identified.

Weiner:

But you get now into quasars and pulsars. Would you say that the optical identification of quasars and pulsars is at the same stage now as the optical identification of the early radio sources was?

Bowen:

Oh, I think so. Well, of course, they are radio sources. In fact, they’re a large part of the radio sources.

Weiner:

No, but I mean that the need for quick identification of them for further study can be compared to the early days of the first radio sources?

Bowen:

Yes, probably. Of course, now usually the identification is pretty straightforward because of the present accuracy of the radio things. Now the question is…well, you look if there’s something there. If there is, if you suspect it’s a quasar, for instance, then the next thing is to get a spectrum and see what its rate of velocity is and so on. But as to the identification, there’s usually not much to it any longer in the way that there was when the uncertainty might be such as an area like this on a sky survey plate.

Weiner:

This brings me to another area altogether and relates to publications of meetings, visits and so forth—the means of communication used first of all within the observatory, whether people got together at Journal clubs regularly or informal colloquia, and then how you related to outside work: whether you brought people in on a regular basis.

Bowen:

Well, we have a Journal club which meets over at Caltech—I think on Wednesday afternoons—and in that are reported any important work done here. And also as we have guest investigators here, we tend to ask them while they’re here to give one of the seminars on what they’re doing or what they have been doing in the last few years. That’s attended, of course, by the staff members, by the graduate students from Caltech and so forth.

Weiner:

So that’s kept up throughout this whole period. There was something similar earlier, too.

Bowen:

Yes, similar in that we had before this joint operation, before the war. There was this sort of Joint club between the astronomers here and the physicists down here known as the Astronomy and Physics Club.

Weiner:

But now it’s all astronomy since there is so much astronomy or astro-physics anyway at Caltech.

Bowen:

Yes.

Weiner:

But nothing here in the observatory building itself?

Bowen:

No. See, we don’t have any meeting hall here big enough for the present group-—that is, when you include graduate students. And also we’re two miles away. A good many of the graduate students don’t have cars, and it’s rather easier to meet over there. As a matter of fact, it’s gotten so big that the meeting hall in the astronomy building isn’t big enough—-we use the one in the biology building.

Weiner:

How large a group is it?

Bowen:

Oh, imagine it’s likely to be a hundred or so that attend. See, there are 16 staff members and usually as many more of Carnegie fellows, National Research Fellows—that is, fellows of various sorts on a graduate level—plus a lot of graduate students and then quite a few of the physicists; that is, men like Fowler and Tommy Lauritsen and Christa been doing a lot of work in the theory of some of these pulsating stars. And Leighton, you see, is in the physics department, but he was elected a member of the National Academy in Astronomy, however.

Weiner:

I notice in the reports that he was pretty regularly a guest investigator.

Bowen:

Yes. But I think he actually is now considered a member of the staff—I’m not sure. He started out on some of these Mars pictures up here, and then he developed this stuff for the radial velocity of the solar atmosphere. He’s an exceedingly clever experimenter.

Weiner:

Now, what about your staff people going elsewhere for a refresher? It seems to me there would be two reasons—one, to come in contact with new people, new ideas, sort of a sabbatical kind of thing; and the other is to go somewhere to use different facilities which are more suited to their own interests.

Bowen:

Well, there is a certain amount of that. I might say, to go back further, one of the reasons we found this guest investigator program so valuable is that in the early days before the airplanes, we were a little bit isolated here on the west coast, and we found that getting these guest investigators out, having them occupy an office here for three months, go to lunch with us and so on, was very valuable. You’ve had a lot of interchange. And with a couple dozen of them coming every year, including a large part of the observational astronomers from the east and even Europe, you’ve got a lot of valuable contacts that way.

Weiner:

That was Millikan’s old approach anyway in Caltech—to bring many people.

Bowen:

Yes. And on the other hand, our people do go…Of course, there are these symposia, a good many symposia now being run, usually under the auspices of the IAU. And our own people do go away quite a lot. For instance, Sandage has just gotten back from a year in Australia at Mt. Stromlo, He spent all of last year there. And he has also spent some time in South Africa. That is, in general the main impulse for doing observing in other places is to go to the Southern Hemisphere, where often there are things that you just can’t get at from up here. That’s the main reason for our people going somewhere else to observe. After all, as far as the Northern Hemisphere, if we can’t do it, no one else can.

Weiner:

So far.

Bowen:

I’m talking now of the last 20 years. So that there’s no particular reason for going to other places in the Northern Hemisphere. There is for going to the Southern Hemisphere.

Weiner:

Another question relating to communication and keeping in touch with this relates specifically to publications. What journals have the staff used mostly in terms of keeping up? Is it the Astro-Physical Journal?

Bowen:

Well, most of our own publications are either in the AstroPhysical or the Astronomical Journal or the PASP.

Weiner:

Publications of the Astronomical Society of the Pacific.

Bowen:

Yes. The PASP is a little bit popularly shaded, tends to be of a little more general interest; and also for fast publication of a short article. The ASP is pretty heavily endowed, so they can get things out in a hurry much more than the Astrophysical can.

Weiner:

What is the background of that? I’m not aware of their endowment.

Bowen:

It’s one of the oldest societies—I think it’s older than the American Astronomical Society—it goes back into the l890s or even before that. I know shortly before Dr. Seares died, they celebrated his 70th year of membership in it, so it goes way back—around 1890 should say.

Weiner:

I know they had a chapter in Chicago, because Hale had some notes that Bob Howard found.

Bowen:

And the journal is quite a little older than either of these other journals. And there have been quite a lot of wealthy people out here: Katherine Bruce and various people have left money to it. They have a pretty big endowment behind it, so that they don’t have to make ends meet on their publications and so on.

Weiner:

But those three publications—Astronomical Journal, Astrophysical Journal and the PASP—have been the main journals.

Bowen:

Yes, they are the main American journals, would guess that 98 of our publications are in those journals.

Weiner:

Well, what journals did you read most in this period, in this past 20-year period?

Bowen:

Well, there are those, and then most of us take the monthly notices—that is of the RAS, So many of the other observatories have their own publications, i.e. a publication of the observatory, although they’re getting away from that in this country. It used to be the case—that a great many of them published their own articles. We had a reprint series that somewhat corresponded to that for us for a while, until we decided to stop it. Then there are one or two French journals. Now all the European journals have gone together into one journal just in the last year. I forget now what they call it. Quite a few of the French publications and so on have joined together. I don’t think the MS has gone into that, but the continental ones have tended to go together into one journal.

Weiner:

I just wanted to get a feeling for that. When you talked about the Astronomical Society of the Pacific, you mentioned the great public interest in astronomy, at least on the part of several wealthy people.

Bowen:

Well, you see, it started out here with Lick. You see, Lick started back around in the 1880s. I know I happened to be at Lick as a Morrison fellow the summer of ‘38 when they celebrated their 50th anniversary. I think that was the completion of the 36-inch refractor.

Weiner:

Well, with the advent of the 200-inch…I mean the 60 and the 100-inch were exciting enough, but the 200-inch was a long time in the making and had been in the public eye for a long time, and was more dramatic than anything that had yet happened and still is. There was, I’m sure, an upsurge of public interest. Now, did this change the observatory program in any way? Was there any special responsibility that you felt toward the public as a result of this interest?

Bowen:

Well, to go back in our history a little bit more, in the early days at Mt. Wilson, they used to open up the 60-inch every Friday night to the public to look through. And that worked up till about the time Just before World War I reasonably well. You’ve never been up the old Mt. Wilson road…

Weiner:

No.

Bowen:

It was Just two wheel tracks carved out along the side of the mountain. You started up, you went into second, you stayed in second ten miles to the top, except occasionally to drop into low. And oh, every quarter of a mile there’d be a turnout where you could pass another car. Once in a while you had to back up a long ways if you happened to run on into somebody between turns. So it was quite an experience getting up there. That was our only road to the mountain up to 1938. And just that road kept our crowds down to maybe 50 or 100. On a Friday night they’d open up as soon as it got dark and stay open until 10 or until they had reasonably covered the crowd. Then every day at 1:30 they would take the crowd that had accumulated onto the floor of the 100-inch and show them around and maybe turn the dome for them or something like that. And week days there wouldn’t be very many people, and on a weekend they might have a hundred or so people to take in. The Carnegie Institution was quite interested in public relations. They also, largely due to Merriam’s influence, put up a small museum up there, which was a building of maybe 30 feet square in which they had around the outside a lot of transparencies, of pictures taken with the telescope. There actually was a lecture hall behind it. Once in a while if they had a large crowd, they’d take them in there and talk to them before they took them over to the other telescope. Well, as I say, this worked well up to 1938. Then in 1938 the state completed a beautiful high-gear road clear to the top. On a Friday night, the first thing that they did was to say, “We’ll insist that you get tickets down here in advance,” and they’d only give out maybe 100 or 200. I think finally they got to giving out 100 tickets for, say, good at 6:30 or as soon as it got dark, or, say, it got dark at seven o’ clock—100 good at seven o’clock and another 100 good at 8:30 or something of that sort. But that didn’t work. You’d get up there, and you’d have 100 very satisfied people and 500 very irate people. The same way they found with the 100-inch—that particularly on a Sunday afternoon they’d just have to take one crowd after another. They couldn’t handle it. Well, fortunately—fortunately for us—about that time World War II came along, and so we just closed down on the basis of saving gasoline. Then after the war, we’d had very good success with the visitor’s gallery at Palomar, where the public come in; they could see the telescope; they were glassed off from any contact with the astronomers; they’d come in and go out—didn’t have any contact with anybody, but they could get a very good view of the instrument. And we usually arranged for somebody there to sell some leaflets about the thing and so on. Well, after the war was over, Dr. Adams, due to the success of the visitors’ gallery, had already arranged for funds to build a visitors’ gallery in the 100-inch. It wasn’t as nice as the 200-inch, because it had to be fitted in after the dome was built. As say, Adams had arranged for the funds, so it was just a question of time to put it in, and it was completed six months or a year after took over. In the meantime, we didn’t open up at all. The other factor why we didn’t feel it was necessary to open up to the public was that a man named Griffith had left to the city of Los Angeles something like a million dollars to put up a fine planetarium in what is known as Griffith Park over here just north of Hollywood. And they put up a fine big building with a lot of exhibits. Some of the Tech people had quite a lot to do with designing them. It had a planetarium, and had a Zeiss 12-inch telescope of the type that’s especially designed for handling people—that is, the eye piece doesn’t move around, It’s pivoted very close to the eye piece. That’s one of our troubles here with our telescopes. You had to crawl people up on ladders, and there was quite a hazard for people who weren’t used to it trying to do it and so on. And as far as looking at what the public wants—namely, the bright objects—something like a 12-inch telescope is actually better than these big ones, That is, the reason for the big ones is to collect light from distant galaxies and so on. You’ve got plenty of light with the planets and the moon, and there, as far as resolving power, a 12-inch will give you all the resolving power that the turbulence of the air will permit anyway. n fact, it tends to be a little better actually, for reasons which won’t need to go into, So that with Griffith available to take care of that need of looking through the telescope, and with our visitors’ gallery up here, we never opened up to the public again. We never opened the 60-inch or any of the other telescopes up to the public again. We felt the need was filled over there. We did keep the museum open showing pictures taken with the telescope. That is, what we’d tell the public was: “We’ll show you the telescope that takes them and we’ll show you the same pictures we look at. We don’t look through the telescope ourselves except just to identify an object. We never do our serious work through the telescope in looking through it.” Which is perfectly true.

Weiner:

You started also, I guess, in the ‘40s—maybe it was later— the series of photographs taken with either the 100 or the 200-inch: the slides and the photographs which are…

Bowen:

That was done right along. We had a catalogue on them.

Weiner:

When did that start?

Bowen:

Oh, that started way back way before my time. You’ve seen these catalogues, haven’t you?

Weiner:

Yes, but I didn’t realize they dated back so far.

Bowen:

Oh, yes, that dated way back before my period.

Weiner:

I see. So that kept up and, of course, became of more and more interest with the dramatic results of the 200—inch.

Bowen:

And, of course, the publicity that that got. There was a good deal of interest in those.

Weiner:

I’d like to explore one thing that we discussed yesterday; and that is that at the time of the shaking down of the 200-inch, the article that appeared in Philadelphia claiming that this was a failure. Would you like to go into that a little bit—-the details of that?

Bowen:

Well, this appeared over the name of a man whom I forget, but I think he was in charge of, or at least one of the important people, at the planetarium in Philadelphia, which I believe was connected with the Franklin Institute… As discussed earlier, we’d had this delay of a year and a half. It wasn’t really a delay. It was the normal time spent in getting a new instrument which was a very advanced instrument, into proper operation and proper adjustment. And he came out with an article in one of those Philadelphia papers—quite a long one, a half-page or page article—saying that the whole project was a failure. We were naturally very much concerned about this, as to its relationship with our various friends. But after discussing it seriously, we decided we wouldn’t try to answer it, because if there were further delays for still some unforeseen reasons, we would be in a difficult spot; and we decided that the thing to do was to wait and let the telescope speak for itself after we had got it into adjustment. We did that, and then of course there was a good deal of publicity as it got into action; and, as I mentioned yesterday, it was just a little bit with that in mind that I gave this speech to the Carnegie trustees and later publishing it in Science as a summing up of what had been done with it and its successes in its first 15 years of operation.

Weiner:

This is your 1964 speech at the time of your retirement.

Bowen:

Yes.

Weiner:

think this might be a good time to ask about your evaluation of that whole period in terms of your directorship which coincided with the first 15 years of operation of the telescope, in terms of the original expectations, what knowledge was obtained. And I don’t mean here for you toA8ver everything that you covered in the article, but to give a more personal view of the satisfactions that you felt or the disappointments.

Bowen:

Well, I think on the whole the telescope did just about what we expected for it. Of course, you never knew what it was going to discover. If you had, there wouldn’t have been any use in doing it. So it’s a little hard to say that it did just what you expected, but certainly it lived up to our expectations for it in getting the answers to a lot of these problems that had been held up earlier. And think on the whole that everybody was pretty well satisfied that it had done what we hoped it would do. There was one other thing I might mention. Of course, there is always a problem in going ahead with a project of this size: to just what extent do you just go ahead and use equipment you’ve got in hand, to what extent do you make real efforts to expand? My own thinking in taking over the project in ‘46 was that the staff of the observatory and a good many of the other engineers and so on had spent a great deal of time between the early ‘3Os and 1952 when it was fully completed, in designing, building first the telescope and then the auxiliary equipment with it. And it was my own feeling that probably for the next decade, the important thing was to cash in on this new telescope with all new equipment rather than worrying too much about any major new equipment. That doesn’t mean that we just lay back and said, “We’re not going to be interested in instrumentation for a while,” because we were continuing things. One of the things we did, of course, was: once the 200-inch was done was to introduce at Mt. Wilson and update all the spectrographs and so on up there in terms of the new developments that had been made at Palomar. And those were somewhat minor things, but it was my feeling that we shouldn’t think in terms, for instance, of going out for funds to build another big telescope or something of that sort, because it seemed that the staff had spent so much time in that development that the wise thing was to cash in on, in terms of astronomical research, what we had rather than making new developments. Of course, there were some things. There were some developments, like the image tube, which has already been described; and so we went ahead on that basis—and I was thinking possibly the next decade, which would have been pretty well up to my time out, time of retirement. You see, that was actually 12 years after that, However, I began to realize around the early ‘6Os that it was getting time that we did some other things. On the other hand, was quite hesitant to start anything, because knew then only had at the most three or four years more. You don’t like to start something then when you know you’re not going to finish it up, because you wonder: “Will I start something that my successor will want to carry through? Will it be what he wants?” It was somewhat with that in view that a little over two years before I retired I wrote letters to both DuBridge and Haskins, who was then president of Carnegie, pointing out the fact that I was due to retire and that they’d better get busy and make a new appointment, get a new appointment in. Well, fortunately they did. One of the troubles, of course, it being a two-institution appointment, because both of them had to approve of it according to the contract between them, it takes a little longer than if one institution makes the final answer. They appointed Dr. Babcock a little over a year ahead, He was appointed think at the annual meeting around May of ‘63, which was about a year and two-tenths. At that time they were talking about this southern telescope. We were talking about a 60—inch up here and so on. So just as soon as Horace was appointed, called him in and said, “Now you’re the one that’s got to carry any of these projects through, particularly this southern project. I would suggest that you spend the next year on that and let me run the routines of the observatory. You just take a free hand and do anything you want in getting that started.” Well, one of the things there was seeing the sites, and my feeling was that if he could go around to Australia and Chile and various places that might be considered and get quite familiar with that, then when he did take over—and the first year he was likely again to be pretty well tied down here learning the ropes—he would at least have the background to direct that from a distance. So it was somewhat with that in mind that I maneuvered that way at the end, because realized that the time was getting short when we ought to start some things, such as the 60-inch down here, although think that was my suggestion, that we needed something of that sort. Also, we were getting computers in down at Palomar, and these image tube spectrographs and the multi-channel thing were started about that time, although those were minor things. Particularly the image tube thing had quite a lot to do with. Oke was the one who was responsible for the other one.

Weiner:

So this didn’t mean any relaxing of duties for you at the end.

Bowen:

No, was shoving over to Horace these new things, because felt he’s the one that’s got to see it through, and consequently he should start them off in the way that he wanted, not the way wanted.

Weiner:

When you look back on the years from ‘46 on, when you look back on all of these developments which we’ve discussed, are there any single things or thing that you can identify as giving you special satisfaction or something that you particularly enjoyed?

Bowen:

Well, don’t know. As far as importance, suppose the most important thing (aid this is something that personally had nothing to do with) was the scale of the universe program—that is, of correcting Hubble’s original distances and then extending it on out with revisions of the Hubble constant and then the quasars coming in, which enabled you to go out still further and all that sort of thing. That is probably the most important thing, although, as I say, that was the thing I had least to do with personally.

Weiner:

Well, of the things that you had to do with personally, is there one phase of it that you enjoyed most and got most satisfaction out of?

Bowen:

Oh, that’s a little hard to say. Of course, as far as my own personal research, did a little followup on the nebular spectra. During this period that I mentioned with the 200-inch, we were taking a lot of pictures—that is, Olin Wilson and I were taking a lot of pictures incidental to breaking it in, and we took quite a lot of nebular pictures, which I was interested in for getting some accurate values for the wavelength of the nebular lines, which unfortunately you couldn’t get from the laboratory, for certain reasons I needn’t go into. Then there were one or two IAU meetings—the one in Moscow I didn’t attend, but nearly everybody else did, so I took over the 100-inch for that period—again on this same program. Of course that I always considered as sort of a fill-in program, nothing of any fundamental importance, but something I rather wanted to finish. And then, of course, the other thing that I was involved in rather heavily from the scientific standpoint was this optical design——the testing of the 200-inch first and then the development of the Coud spectrograph, pushing it to the very limit that you could get with the Schmidt and making certain modifications to push it still further. Then, of course, in recent years I’ve been working largely on developing this optics for use with the image tube, which has been fun, but I realize perfectly well it’s a pretty routine project. It happened to use some skills that I developed when I was teaching a graduate course in optics at Tech. But there’s nothing of any fundamental importance.

Weiner:

It’s needed. It’s important and you enjoy doing it. That’s part of it. You get satisfaction out of doing it.

Bowen:

Oh, yes, I enjoy doing it. It keeps me amused. But on the other hand, I realize perfectly well that there are no fundamental new discoveries or anything like that.

Weiner:

You’ve had a few in your time. So this is the work that you have been pursuing since your retirement, mostly optical.

Bowen:

Yes. Well, that and, well, the other thing was the design of this new 60-inch. You asked about the success of the 200-inch. The one thing that we’ve been a little disappointed in the 200-inch is the field of view for direct photography. It will cover about half the diameter of the moon on one plate, and it has a field just about that big around, which means that it’s completely inadequate ... If you have to search for something—say, one of these radio sources—it’s just too small a field. It takes too many plates to cover it. And one of the big things we’ve been trying to get out of this 60-inch is a bigger field, and we are getting a field which has 25 times that area. It will require longer exposures, but, on the other hand, 25 times makes up for a lot of them — serves a longer exposure, which is around six times as long. I think it will be very useful to do that. Again the design isn’t fundamentally my own. It’s a Ritchey-Chretien plus a Gascoigne corrector, but it did involve quite a little doing to get the design just right.

Weiner:

And this is something you’re involved in just about every day.

Bowen:

Well, as I think I mentioned yesterday, this is the first large telescope that our present head of the optical shops tackled. And testing these large things involves a lot of new techniques different from what you do when you’re building small optics. And he is not familiar with a lot of these…that is, you’ve really got to go over it and survey that surface… Well, for instance, here is a survey of it. These are cross sections across it at every 30 degrees around. This is a plot of the deviation of the thing from its true theoretical surface, He’s pretty good. This is one micron. This much is one micron error; and you see that no place does ft go that much off, But it’s got to go a lot better than that before we’re satisfied with it, But about the only way to do it is to do this, actually measure it, measure the surface. And particularly in this case, it’s a high order equation, which means that it’s a hyperboloid, not a paraboloid. If this doesn’t come out a straight line, you then have to put into these calculations after you’ve made your Hartmann. Then you have to put in these various corrections to bring it back to what it is. So it’s something that you pretty well have to understand the theory of the thing as well. And Floyd Day, who is in charge, is a very fine technician, but he’s not a theoretical optician. Between us we get along pretty well, don’t know what kind of rouge to use and so on or just how long to polish to take off a tenth of a micron, which he does; so that between us we’ve managed to get along pretty well, But unfortunately it takes the both of us.

Weiner:

You also don’t know how to retire obviously.

Bowen:

Well, I think you’d agree that it’s a whole lot better to do this than sitting around doing this [being interviewed].

Weiner:

I think perhaps that we should retire, unless there is something specific that you want to talk about.

Bowen:

No, I think that covers the subject. At least I feel pretty well talked out.

Session I | Session II