combination giving a different telescope focal length and focal ratio. With a
secondary other than the one designed for the Cassegrain focus, the telescope
focus is usually located at a different physical position. For a telescope in an
equatorial mount plane mirrors redirect the light, with the final beam directed
along the polar axis of the telescope to the so-called Coude focus. For a telescope
in an altitude-azimuth (alt-az) mount a plane mirror directs the light along the
altitude axis to the so-called Nasmyth focus. In both cases m and jS are usually
larger than at the Cassegrain focus.
For a classical telescop ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month, and much more.