An alternative, versatile, high-tolerance design of a modified Richter–Slevogt camera, using standard glasses

Abstract

Prime-focus catadioptric astrographs have been used for a long time in various astronomical applications. The prime advantage offered by them is the capability to produce remarkably wide fields of view, and hence generate a huge amount of data in relatively less observation time. An emerging application of such wide-field astrographs is in the form of telescope arrays. While this has been implemented mostly, using commercial refractive lenses, low-cost catadioptric objectives can be used as an alternative for wide-field or high-contrast array applications. Commercial catadioptric systems are generally available as modifications of Schmidt and Maksutov systems, that too, mostly in the Cassegrain configuration. Here, we present a low-cost alternative prime focus camera design of Richter–Slevogt configuration, which is in turn an extension of the Houghton correctors. The Richter–Slevogt design has the potential for a very high performance due to several degrees of freedom. The presented one is a 150 mm aperture, $f/3$ system, providing 3.5° (circular) diffraction-limited FOV (strehl $\ge 0.85$), using only standard glasses, N-BK7 and F2. We present the performance analysis, tolerance sensitivity, and statistical (Monte-Carlo) analysis for this design. Potential applications of the system, other than as an array are also briefly discussed.