Cassegrain Nasmyth

The Cassegrain Nasmyth telescope has the same optical design as the classical Cassegrain telescope except for a small tertiary mirror which sends out the light on the side of the telescope tube instead of through a hole in the primary mirror.^[1] This design is common in large telescopes, e.g., the W. M. Keck Observatory.

This telescope was built for visual work, but is also used with different CCD detectors. Optical design 0.61m f/15 Cassegrain Nasmyth... Observatory code 238. Oslo Norway

Figure 1 shows the light-path from a star based on the 0.61m telescope in Oslo. Figures 2 and 3 show the use of a focal reducer, flip mirror unit, ocular and CCD camera. See also: Nasmyth telescope.^[2]