Wide-field Corrector for a Gregory Telescope

A form of prime focus corrector for the Gregory system is proposed that provides the sub-arcsecond field of view up to 3 in diameter for the spectral range 0.35 − 0.90 microns. The corrector includes five lenses made of same glass (fused silica is preferable). The distinctive feature of the corrector consists in dissimilar use of the central and edge zones of a front lens disposed in the exit pupil of a two-mirror system. As an example, the f/1.9 telescope is considered with the 6.5-m aperture and the total length 8.8 m. Its primary and secondary mirrors are pure ellipsoids close to concave paraboloid and concave sphere, respectively. In the basic configuration, all surfaces of the corrector are spherical. The diameter of a star image D80 varies from 0 .25 on the optical axis up to 0.50 at the edge of the 2.3 field. Only slightly worse images shows spherical corrector for the 2.4 field of view. The fraction of vignetted rays grows on 1.7% from the center of field to its edges. Aspherization of some lens surfaces allows to reach subarcsecond images in the field of 3.0 in diameter. c © 2006 MAIK “Nauka/Interperiodica”.