Houghton anastigmatic telescope containing aspheric mirrors that allows corrector position as a free parameter

A family of catadioptric telescopes is investigated, characterzied with two-element, full-aperture afocal corrector lenses and aspherical, focusing, primary mirrors or primary-secondary mirror combination. Third-order aberration and design equation are provided for anastigmatic systems in which corrector position must be a free parameter, forcing the consideration of aspherics on the mirrored surfaces.