Ritchey–Chrétien optics(rich -ee kray-tyan ) An optical system that is a variation on the Cassegrain configuration and was developed between 1910 and 1920 by George Willis Ritchey and Henri Chrétien. It corrects both spherical aberration and coma at the Cassegrain focus, and therefore gives a high-quality image over a relatively wide field of view. A primary mirror with a hyperbolic profile is used in conjunction with an appropriate departure from classical (hyperbolic) form at the secondary mirror.
Ritchey-Chrétien optics[′rich·ē ′krā·chən ‚äp·tiks]
A modification of the Cassegrain optical system used in large optical telescopes; it has a hyperbolic image-forming primary mirror, no spherical aberration, and no coma; it has a larger usable field than either Newtonian or Cassegrain optical systems.