The optical design of a mirror telescope with a free aperture of 3.5 m is described. Observations can be made in the Cassegrain (RC) focus f/8, in the direct focus f/3, and in the coudé focus f/30. The results of ray tracing in the form of spot diagrams are dealt with. Some technological problems are discussed.
H. Köhler, "The Optical System for the 3.5-m ESO Telescope," Appl. Opt. 7, 241-247 (1968)