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Honeycomb Mirrors of Borosilicate Glass; Current Results and Plans for 7–8m Diameter

Published online by Cambridge University Press:  12 April 2016

J.R.P. Angel ,
D. Arganbright ,
L. Harmonson ,
J.M. Hill  and
N. Woolf
J.R.P. Angel
Affiliation:
Steward Observatory, University of Arizona
D. Arganbright
Affiliation:
Steward Observatory, University of Arizona
L. Harmonson
Affiliation:
Steward Observatory, University of Arizona
J.M. Hill
Affiliation:
Steward Observatory, University of Arizona
N. Woolf
Affiliation:
Steward Observatory, University of Arizona

Extract

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The case for making large mirrors for astronomy with borosilicate glass honeycomb structure has been made in an earlier paper (Angel and Hill, 1981). Honeycomb structure gives rigidity in a lightweight mirror as well as low thermal inertia. Mirrors which are in thermal equilibrium with the air hold the promise of better images, since convection at the mirror is eliminated. Thermal expansion of borosilicate glass is problematical in thick mirrors which are likely to be out of thermal equilibrium and hence distorted. This will not be a problem in honeycomb mirrors with thermal time constants of only a few minutes. We believe a single casting technique holds the greatest promise of making borosilicate honeycomb mirror blanks up to 7 meters in diameter. Our work to develop the technique now involves casting test blanks 60cm in diameter but which have the full thickness (33cm), cell size (15cm) and faceplate thickness (2.5cm) needed for a 1.8m mirror.

Type
Section I: Optical Telescopes, Existing And Planned
Information
International Astronomical Union Colloquium , Volume 67: Instrumentation for Astronomy with Large Optical Telescopes , 1982 , pp. 33 - 36
Copyright
Copyright © Reidel 1982

References

Angel, J.R.P. and Hill, J. 1981, Proceedings of the ESO Conference on Scientific Importance of High Angular Resolution at Infrared and Optical Wavelengths, Garching, 24–27 March 1981.Google Scholar