Catadioptric Telescopes

A catadioptric optical system is one that employs both lenses and mirrors to focus the image.  Perhaps the most popular catadioptric among amateur astronomers, the Schmidt-Cassegrain Telescope (or SCT) uses a combination of spherical primary and secondary mirrors, along with a corrector plate (lens) that helps correct for aberrations.  You’ll spend a little more money on this design because it’s more complex to build than a reflector, but the combo of aperture and transportability is hard to resist.