Wide-Eyed Camera

More exciting to astronomers than a flaming new comet is the Schmidt star camera. It will clearly photograph 500 times as much sky as the small area (1DEG in diameter) now recorded by ordinary reflector telescopes, yet it requires an exposure only one-tenth as long as the fastest astronomical lenses previously used. Equally valuable in aerial photography for its speed and wide, clear focus, the camera is being adopted by the U.S. Army.

Inventor of the camera, the late Bernhard Schmidt of Germany's Hamburg-Bergedorf Observatory first described the device in 1931, but with uncooperative vagueness unusual in a scientist. U.S. astronomers--mostly amateurs--grasped Schmidt's hints, figured out how his lens, reflector and film must have been designed and assembled. When they had cleared up details in several experimental models, major U.S. observatories began building larger Schmidts. The biggest (24-36 inch) was dedicated last fortnight at Cleveland's Warner & Swasey Observatory, and others are nearing completion this week at Harvard, Mt. Palomar, Tonantzintla, Mexico.

Though astronomers still gaze at the stars, most telescopes are now in effect cameras. Essential part is a concave spherical mirror which gathers starlight, focuses it on a photographic plate. But mirrors hitherto could focus light from but a small section of sky on the plate without fuzzing and distortion. In the Schmidt camera, however, the light rays pass through a concave-convex lens which aims them at the mirror at such angles that they are reflected upon the plate in sharp focus (see diagram). Photographs of distant, dim nebulae formerly required exposures of 50 hours--five hours a night for ten nights. Now they can be made in a single night.

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