a catadioptric telescope designed to produce a very sharp image of a large area of sky in one photographic exposure. It incorporates a thin specially shaped glass plate at the centre of curvature of a short-focus spherical primary mirror so that the resulting image, which is focused on a photographic plate, is free from spherical aberration, coma, and astigmatism
Word origin
C20: named after B. V. Schmidt (1879–1935), Estonian-born German inventor