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Astronomy In California 1850 – 1950:
Telescope Makers, Telescopes, and Artifacts
Schmidt Camera
By Charles A. & Harold A. Lower, California Telescope Makers
The most successful short-focus photographic telescope is the Schmidt Camera, first described in 1932 in a paper by Bernhard Schmidt of the Hamburg Observatory in Germany. Schmidt's life is as interesting as the novel optical system he introduced. His excellent work became known to professional astronomers and leading optical houses, yet the individualistic and independent Schmidt resisted all offers of full-time employment. It was not until 1926 that Dr. Schorr, director of the Hamburg Observatory, persuaded him to live at the Hamburg Observatory and to participate in its work on a volunteer basis. Here, Schmidt worked on new types of telescope mountings and drives, and in 1930, constructed his first camera. The camera he introduced, generally referred to as the basic "Schmidt Camera," consists of a concave spherical mirror in front of which is a thin and optically weak corrector plate. It is an ingenious mirror/lens combination that gives a coma-free image with no astigmatism. Applied to the stars, the camera gave round stellar images on curved film over a field as large as 16 degrees of angular diameter. Bernhard Schmidt died in 1935.
The first Schmidt Camera outside of Germany appears to have been the f/2.4 system made by Dr. Page Bailey of Riverside, California in 1932. This was followed by the 8-inch Schmidt Camera made by Charles and Harold Lower in San Diego, California in 1936. But the Schmidt Camera achieved perhaps its greatest success in the 48-inch Schmidt at Mount Palomar Observatory in Southern California. At 48 inches of clear aperture, it is one of the largest wide-field cameras in the world. For many years after its installation, the main work of this telescope camera was the Palomar Sky Survey. The Survey was completed in 1959 and copies of the photographic plates (taken in both red and blue light) have been used worldwide for research and discovery.
The Schmidt Camera in this exhibition is the Charles and Harold Lower Schmidt Camera completed in 1936. Charles and Harold Lower (a father-and-son team) were unemployed amateur astronomers and telescope makers in San Diego, California. In 1932, D. O. Hendrix, an astronomer at the Mount Wilson Observatory, gave a lecture on the Schmidt optical principle to the Riverside Astronomical Society. The lecture inspired the Lowers to build the instrument even though they did not have all the necessary details. Nevertheless, the camera was completed in January 1936. Harold Lower wrote: "So far as I know, our Schmidt is the first f/1 Schmidt. I believe that it is also the largest f/1 in the world. It covers a wider field than any other Schmidt which I have heard of so far. (It has a 20-degree field of view.) Our methods of testing were new and original."
The Lower Schmidt Camera is in a varnished plywood box, 27 inches long, 14 1/2 inches square. The interior is painted black. It has a 10-inch opening, with a plywood cover. A hinged door (8 inches wide, 12 inches long) gives access to the interior. The corrector lens is 8 inches in diameter, 3/16 inch thick at the edge. The mirror is 12 inches in diameter and made of Pyrex. Since the Schmidt is exclusively a photographic instrument, there is no eyepiece. The film was mounted on a curved plate, which was positioned directly at the focal surface. The film holder is missing. Opposite the Schmidt instrument is a 7- inch Cassegrain telescope.
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