Newtonian focus

Newtonian Focus
Related Category: Astronomy: General
see telescope.
More on Newtonian Focus
Telescope - traditionally, a system of lenses, mirrors, or both, used to gather light from a distant object and form an image of it.

Newtonian Focus
A focal arrangement of a reflecting telescope in which a diagonal mirror reflects light out the side of the telescope for easier access
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Newtonian focus - An optical arrangement in a reflecting telescope, in which a flat mirror intercepts the light from the primary mirror before it reaches the focus and reflects it to a focus at the side of the telescope tube.

While the Newtonian focus design is still used in amateur astronomy, professionals now tend to use prime focus, Cassegrain focus, and coudé focus designs.

7 Four reflecting telescope designs: (a) prime focus, (b) Newtonian focus, (c) Cassegrain focus, and (d) coudé focus.

Most large research telescopes can operate as either a cassegrainian (longer focal length, and a narrower field with higher magnification) or newtonian (brighter field). They have a pierced primary, a newtonian focus, ...

either convex, to reflect the image out of a hole in the bottom of the telescope to the Cassegrain focus or along the telescope mount axis to the coudé focus; or flat, to reflect the image out of the side of the telescope to the Newtonian focus.

See also: Astronomy, Telescope, Light, Focus, Second