Schmidt-Newton telescope

A Schmidt-Newton telescope (sometimes abbreviated SNT) is a variation on a Newtonian telescope in which the light first passes through a particular kind of lens (Schmidt corrector plate) followed by a spherical primary mirror, then a flat, angled secondary mirror (fold mirror). As such, it is also a variation on a Schmidt camera. The corrector plate reduces spherical aberration, giving it less coma than a reflector telescope that incorporates a parabolic mirror, making shorter focal lengths useful. The presence of a lens with the size of the aperture and primary mirror adds a challenge to making large (research) telescopes with the design. Current amateur telescopes include models with this design.