Mirror support cell
In astronomy, a mirror support cell - more commonly mirror cell - is a component of a reflecting telescope that supports the mirror in place to hold optical alignment, allow collimation adjustment, and protect it from falling out. The common usage of the word denotes the cell that holds the primary mirror, however technically it could also be used to denote the support assembly for the secondary mirror or other mirrors.
Overview
Basic cells
A basic mirror cell can be built using minimal calculation and simple materials. Only slightly more complex are the wooden, plastic or metal cells which are often glued and which are either not user adjustable or which have only limited adjustment and which are used in lower end commercial telescopes and smaller amateur-built telescopes.Cells for more sophisticated "small" telescopes
Telescope makers seeking to build larger "small" telescopes with thinner mirrors find simple designs inadequate so they must resort to more complex design methods which include possible use of multiaxis adjustment potential and floating whippletree cell design, often optimimized using computer aided design programs. There remains a good deal of discussion in the amateur telescope making community over the use of glue and the addition of simple astatic devices in such cells.Image:GTC Active Optics Acutators.jpg|thumb|left|Actuators of the active optics in the mirror support cell of the Gran Telescopio Canarias.