A new family of 2 mirror unobscured telescopes of compact "Schiefspiegler", off axis Cassegrain geometry,
incorporating aspheres, tilted and decentered secondary, and tilted focal surfaces, will serve as fast, high resolution,
moderately wide field telescopes / collimators. Designs range from f/5 to f/16. The nCUB designs provide a focal
surface normal to the gut ray for visual use. The tCUB designs provide collimator telescopes with focal surfaces tilted
so that any light reflected from the reticle is eliminated.
Richard F. Horton,
"A family of 2 mirror unobscured wide field telescope and collimator designs", Proc. SPIE 7652, International Optical Design Conference 2010, 76520M (4 February 2011); doi: 10.1117/12.871072; https://doi.org/10.1117/12.871072