Study of aberrational performance of Klevtsov family of sub-aperture catadioptric telescopes and field correctors for them

摘要

Study of aberrational performance and manufacturing tolerances of Klevtsov family of optical telescopes is presented, with focus on determination of practical boundaries in design space of two-glass solution, which provides correction of spherochromatic aberration comparable with complex full-aperture catadioptric designs at expense of using dense and ultra-dense crowns for sub-aperture meniscus elements with careful mating of Mangin mirror glass. This allows radical improvement of spherochromatic correction in comparison to basic Klevtsov design with corrector lenses of same glass, with increase of both primary mirror's and whole system's speed. This family of designs is subject of late Klevtsov's patents from middle of 90's and allows building of very compact systems with moderate overall focal ratio, like presented analyzed examples with 0.5 m aperture with f/1.5 primary mirror and f/5 equivalent focal ration, with diffraction-limited on-axis performance within whole visible range Comparison of practical Klevtsov designs with pure reflective designs such as Cassegrain, Ritchey- Chretien, Dall-Kirkham and full-aperture catadioptric designs such as Schmidt-Cassegrain, Maksutov-Cassegrain and Volosov-Houghton designs is taken for field and axial aberrations correspondingly. A number of field correctors for Klevtsov telescope is presented, with near-neutral and focal-converting designs. Overall combination of investigated basic variants and correctors forms perspective multi-focal all-spherical optical telescope, highly suitable for large-volume production, combining low cost, short optical tubes, moderate secondary mirror obscuration and decent field for both high-quality visual observations and CCD imaging.