Optical Design: True Ritchey Chrétien / RC by GSO
Ritchey Chretien systems are excellent Cassegrain-configuration optical systems which are great performers for many different types of astronomical observation, but are particularly well suited for astrophotographic purposes. The RC has a concave hyperbolical primary mirror and a convex hyperbolical secondary mirror.
Contrary to Maksutovs or Schmidt-Cassegrains which have spherical mirrors and need image correctors, and contrary to Newtonians that need coma correctors, the RC system is a well corrected photographical instrument that uses only mirrors (no false colour!) and does not require any corrector with many cameras.
Hyperbolic RC system is superior to a standard Schmidt-Cassegrain and other optical designs in many important respects: a well-designed RC will have no Coma (elongation of stars) around the edge of the field; an RC will give a sharper on-axis response than most SCTs or Newtonians; they are completely false colour free; they have no front corrector plate, thus reaching thermal equilibrium quicker and cutting down dramatically on dewing issues.
The resulting image correction throughout the field as well as the sharpness on the optical axis are superior to typical Schmidt-Cassegrains or Newtonians.