The optical designs of three CCD cameras for the Keck Observatory spectrometers are described and illustrated with drawings and diagrams. The 8-element camera for the Low-Resolution Imaging Spectrometer (LRIS) has focal length 12.0 inches, entrance aperture 8.9 inches, and flat FOV diameter 2.93 inches; the camera is color corrected without refocusing over the spectral range 390-1000 nm. For the High-Resolution Echelle Spectrometer (HIRES), a larger and a smaller version of a 30-inch-focal-length camera have been designed. Each camera is color corrected at 310-1100 nm and comprises a single-element corrector, a concave mirror, a contact triplet field-flattening element, and a flat vacuum window. The smaller design, with 28.7-inch entrance aperture and flat FOV diameter 3.15 inches, has been selected for construction.
Harland W. Epps,
"Camera designs for the Keck Observatory LRIS and HIRES spectrometers", Proc. SPIE 1235, Instrumentation in Astronomy VII, (1 July 1990); doi: 10.1117/12.19118; https://doi.org/10.1117/12.19118