Making a Monolithic Telescope Part 1: Optical Design and Aspherics. - YouTube
Since a Cassegrain reflecting telescope has a hole in the center of the main mirror, doesn't it have a hole in the center of its field of view? - Quora
Optical system of aplanatic telescope with a 100 m spherical primary mirror
US8134778B2 - Monolithic eccentric Mersenne-Cassegrain telescope - Google Patents