SCT reflector telescopes use an exotic looking "corrector plate" (lens) to compensate for the easier-to-produce spherical mirrors vs parabolic. https://en.m.wi

SCT reflector telescopes use an exotic looking "corrector plate" (lens) to compensate for the easier-to-produce spherical mirrors vs parabolic. https://en.m.wikipedia.org/wiki/Schmidt_corrector_plate https://en.m.wikipedia.org/wiki/Schmidt_corrector_plate