Telescopes can suffer from a variety of aberrations which are inherent in different optical designs. There are six primary aberrations to worry about: spherical aberration, distortion, coma, astigmatism, field curvature and chromatic aberration.
All telescopes are corrected for spherical aberration, and distortion is not a problem over the relatively narrow fields produced by telescopes. Coma causes stars to take on an asymmetric comet-like shape off axis. Coma is inherent in Newtonians, classical Cassegrains, and most Schmidt-Cassegrain telescopes. By using an aspheric mirror or corrector lenses, some SCTs eliminate coma. The Ritchey-Chrétien (RC) deisgn uses two hyperbolic mirrors to eliminate coma. But RCs still suffer from astigmatism and field curvature, causing enlarged star images over a large field.
The Hyperion telescope does not suffer from coma, astigmatism or field curvature. By using an afocal (zero-power) corrector lens system, it can correct for all these aberrations without inducing chromatic (color) aberration. The design uses a parabolic primary mirror and spherical secondary mirror. The corrector lens consists of two elements located in the primary baffle tube. The Hyperion truly delivers the best image quality over the largest possible field of view.