Diorama housing the original Newtonian mirror cage from the 100-inch Mount Wilson reflector, on loan from the Carnegie Institution of Washington. Edwin Hubble is at the Newtonian focus. Eric Long photograph, National Air and Space Museum.

Soon after the original Herschel 20-foot tube arrived at the National Air and Space Museum on loan from the National Maritime Museum, staff photographer Eric Long took a series of documentation photographs. For this one, curators placed the original 18.5-inch speculum metal mirror at the base of the tube, kept the access door open for illumination, and Eric photographed what an observer would see from the top end of the tube in "daylight," from what has become known as the Herschelian focus. Eric Long photograph, National Air and Space Museum.

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