Brief historical remarks concerning one type of wide-field catadioptric telescopes

As it is clear from its name, the telescope has 300-mm aperture and 7° (52.1 mm) field of view. The optical layout of the f/1.44 telescope consists of a three-lens front corrector, two mirrors, and a two-lens rear corrector. All surfaces are spherical nevertheless the design yields sharp images: the RMS spot diameter is less than 4 μm (1′′.9) in the integral light 0.42 – 0.84 μm. The diameter of the flat field corresponds well to a diagonal of commonly available CCDs. In this connection, the TEC and author of the optical design have obtained a number of requests concerning historical roots of the optical scheme. The following short remarks do not claim to be an exhaustive review of this extensive topic; the only goal was in noting some important steps which have led to the creation of a three-lens corrector to a spherical mirror. Undoubtedly, this cursory glance on such an extensive topic requires further development and specification.