Schmidt-Cassegrain Telescope

The Schmidt-Cassegrain telescope is a very popular design for amateur astronomical telescopes for its high contrast and low aberration effects. It consists of a Schmidt corrector plate and a Cassegrain reflector. The Cassegrain reflector is made up of a concave primary mirror for focusing the light and a convex secondary mirror that redirects the light back through a hole in the primary. This provides a long focal length even with a short tube length. The Schmidt plate itself is an aspherical lens used to correct spherical aberrations.