A wide-field telescopic camera first made in 1930 by the Estonian optician Bernhard Voldemar Schmidt (1879–1935); also called a Schmidt telescope or simply a Schmidt. It uses a spheroidal primary mirror with a thin corrector plate at its centre of curvature which eliminates spherical aberration. The focal surface is curved and lies within the instrument, which means that photographic plates or films must be curved accordingly. A Schmidt has a very wide field of view free from astigmatism, distortion, and coma (see coma, optical). Large Schmidt cameras are used for sky surveys. The quoted aperture of a Schmidt camera is that of its corrector plate; the mirror is always larger.
Subjects: Astronomy and Astrophysics.