| a wide-angle reflecting telescope used primarily for astronomical photography, in which spherical aberration and coma are reduced to a minimum by means of a spherical mirror with a corrector plate near its focus. |
Schmidt telescope
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 distortions-namely, spherical aberrations-produced 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.
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