An ƒ:1.0 spectrograph camera with a nearly flat field was designed by splitting the symmetrical ball lens of Sutton and adding correcting components. The resulting 7-element objective has longitudinal spherical aberration not exceeding 0.001 mm between 7000A and 9000A.
The camera is constructed so that all adjustments of tilt and focus are made from behind the plate-holder. The plate emulsion is kept within 0.025 mm of the focal plane even when the camera is operated upside down.
In astronomical use the camera photographs several hundred angstroms of spectrum at one time on flat plates, with good definition through the range 4000A to 9000A. As compared to modified Schmidt cameras, it has the disadvantage of a field limited to 7 degrees by vignetting, but is comparable in light efficiency, and has the greater convenience of allowing the use of glass plates large enough to carry multiple exposures.
ABE OFFNER and WILLIAM B. DECKER, "An ƒ:1.0 Camera for Astronomical Spectroscopy," J. Opt. Soc. Am. 41, 169-169 (1951)
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