Mirror support cell

This article is about telescope mirror support cells. For the neurological colloquialism "mirror cell", see Mirror neuron.
Mirror of the Large Binocular Telescope

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 (M1), however technically it could also be used to denote the support assembly (usually called a spider or strut) for the secondary mirror (M2) or other mirrors.

Overview

Basic cells

A basic mirror cell can be built using minimal calculation and simple materials.[1] 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[2] cell design, often optimimized using computer aided design programs.[3][4] 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.

Actuators of the active optics in the mirror support cell of the Gran Telescopio Canarias.

Cells for large telescopes

Astronomical observatories require a much heavier and more complex mirror support cell. One notable example of the structure needed for such telescopes is the dual cell for the M1 mirrors of the 8.4 meter Large Binocular Telescope at Mount Graham International Observatory. This is a multiple beam and truss system which in turn supports a temperature maintenance and air flow system, six position actuators and the 160 pneumatic actuators which work its active optics system. This results in a huge assembly structure weighing about 28 tons without its mirrors. Such a mirror cell requires multiple mathematical steps of finite element analysis of its deformation under static and moving loading.[5][6]

See also

Notes

  1. ^ Pierce, J. M. (1926). "A telescope that anyone can make". In Ingalls, Albert G. (ed.). Amateur Telescope Making, Book One. Scientific American. pp. 94–102.
  2. ^ [1] Grubb 15 inch support cell built in 1835
  3. ^ Holm, Mark. "Mirror Cells for Amateur Telescope Makers". Archived from the original on February 11, 2006. Retrieved November 21, 2009.
  4. ^ Kriege, David; Richard Berry (June 1997). The Dobsonian Telescope, A Practical Manual for Building Large Aperture Telescopes. Willmann-Bell. pp. Chapter 5. ISBN 978-0-943396-55-2.
  5. ^ Miglietta, L. (1996). "The Final Design of the Large Binocular Telescope M1 Mirror Cells". Other LBT Publications. Proceedings of SPIE conference on Optical Telescopes of Today and Tomorrow, 2871, (1996). Archived from the original on 2004-08-29. Retrieved 2009-11-20.
  6. ^ "UA-95-02: Mirror Support System for Large Honeycomb Mirrors". Large Binocular Telescope Project Technical Memo. University of Arizona. 1995. Archived from the original on 2010-07-03. Retrieved 2009-11-20.