A Schmidt Camera (or Schmidt Telescope) is a Reflector Telescope with a spherical Primary Mirror and a lens to correct the spherical Aberration (called the Schmidt Corrector Plate). They are relatively easy to construct at a given size, because spherical mirrors are easier to grind and they produce relatively little other aberration usually associated with a short Focal Length, thus can be made with a wide Field of View, which is especially suitable for Surveys. However, the Focal Plane is, in fact, not planar but curved, thus requiring unique design of the image recording, such as curved photographic paper in the photography age. The general design of the Schmidt camera was developed by Bernardt Schmidt in 1930. Variants of the Schmidt camera combine it with other telescope designs, e.g., the Schmidt-Newton Telescope.
ESO/Uppsala Survey Of The ESO (B) Atlas
Palomar 48 Inch Telescope (P48)
UK Schmidt Telescope (UKST)