SCHMIDT TELESCOPE

also called Schmidt Camera, telescope in which a spherical primary mirror receives light that has passed through a thin aspherical lens, called a correcting plate, that compensates for the image distortionsnamely, spherical aberrationsproduced by the mirror. The Schmidt telescope is thus a catadioptric telescope; i.e., its optics involve both the reflection and refraction of light. Because the Schmidt telescope uses a spherical collecting mirror instead of a paraboloidal one (as conventional reflecting telescopes do), it is free from astigmatism and so has a wide field of view. The Schmidt instrument can, in effect, provide a sharper image of a larger area of the celestial sphere than ordinary reflectors and is thus ideal for star surveys. The device was invented in 1930 by Bernhard Schmidt (q.v.) of the Bergedorf Observatory, Hamburg. The Schmidt-Maksutov telescope, invented by D.D. Maksutov in 1941, is similar in design and purpose to the Schmidt telescope but has a spherical meniscus in place of the correcting plate of the Schmidt.