Cassegrain Telescopes


Cassegrain Telescope ray diagram

A ray diagram of a Cassegrain Telescope

The light enters the telescope from the left and is focussed by reflecting off the large, concave (curves inwards) Primary Mirror.

A convex (curves or bulges outwards) secondary mirror is then used to move the focus right down through a hole in the centre of the primary mirror. This is a very good place to put an instrument on a big telescope.

Most modern professional telescopes are of this type, including the Liverpool Telescope.

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