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Baker–Nunn camera(bay -ker nun) A wide-field astronomical camera, similar to the Schmidt camera (see Schmidt telescope), designed for satellite tracking. It uses a spherical primary mirror but replaces the Schmidt correcting plate with a three-element achromatic correcting lens.
an apparatus for photographing artificial earth satellites against the background of stars; it is also called a satellite camera. The optical system is the Schmidt system with a tricomponent correcting system; the diameter of the correcting lens measures 508 mm, and the aperture ratio is 1:1. The focal surface is almost spherical in shape; the angular dimensions of the frame are 5 × 30°. The camera is mounted on a base having vertical, horizontal, and orbital axes. Such a system permits the optical axis of the camera to inscribe any large circle with an angular velocity ranging from 0 to 7,000’’/sec. The shutter is of an obturator type, and its performance is registered to an accuracy of 0.0001 sec. The satellite’s position is registered on a photograph to an accuracy of 2–3’’. The camera is named after the American firms that manufacture the optical and mechanical parts of the instrument (J. Baker and J. Nunn, respectively). It was constructed in the USA in 1957 by F. L. Whipple and J. A. Hynek.
A. M. LOZINSKII