Design procedure for ritchey-chrétien corrector.

A four-lens corrector system to remove residual aberrations in a Ritchey-Chrétien telescope was selected as the means of studying the relative effectiveness of two design methods: a ray deviation error function and third order aberration theory. At several stages in the design, very significant improvements were made by switching from ray deviation results to aberration theory and then back to ray deviation design. The goal, a 300-cm focal length, f/10 diffraction-limited 1.2 degrees flat field telescope for white light, was achieved. Lens data and system performance, including computed spot diagrams, are given for eight versions.