Schmidt camera

The Schmidt telescope corrects for the distortion caused by large telescopes by using a corrector plate, a small glass object with a complicated shape that could be placed near the focus of a spherical mirror. These telescopes were usually used in conjunction with a photographic plate rather than an eye.
 Bernhard Voldemar Schmidt Germany 1930 Schmidt camera

The Schmidt telescope corrects for the distortion caused by large telescopes by using a corrector plate, a small glass object with a complicated shape that could be placed near the focus of a spherical mirror. These telescopes were usually used in conjunction with a photographic plate rather than an eye.