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Proceedings Paper

Monolithic Mirror Substrates Of The 8-M Class And Lightweight Mirror Substrates Manufactured From The Glass Ceramic Zerodur
Author(s): Hartmut W. Hoemess; Rudolf Mueller; Erich W. Rodek; Friedrich B. Siebers
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Paper Abstract

For about 20 years Schott has been supplying the glass ceramic ZERODUR, a material with very low thermal expansion. Besides many other applications ZERODUR is excellently suited for the manufacture of mirror substrates for telescopes. About 80 % of all telescopes in the western world with mirror diameters p1.8 m have been equipped with ZERODUR during the last 10 years. The development of modern astronomical telescopes is aimed at larger primary mirrors and extremely lightweighted secondary mirrors. New techniques have been developed by Schott for the manufacture of thin monolithic mirror blanks of more than 8 m in diameter. The development of thin meniscus shaped shells using the spin casting technique was successfully completed last year. During a test production several mirror substrates up to 4.1 m in diameter and down to 57 mm in thickness could be produced. The know-how has been acquired for the fabrication of mirror substra-tes of more than 8 m in diameter by the spin casting technique. Schott has also performed considerable developmental work in the field of lightweighted ZERODUR mirror substrates which can be generated using different techniques: forming of the lightweighted structure during casting, fusion of individual components to a total structure and lightweighting of a massive block by various mechanical machining methods. Several samples have been produced with diameters up to 0.7 m and weights per unit area down to approximately 60 kg/m2.

Paper Details

Date Published: 13 April 1989
PDF: 5 pages
Proc. SPIE 1013, Optical Design Methods, Applications and Large Optics, (13 April 1989); doi: 10.1117/12.949380
Show Author Affiliations
Hartmut W. Hoemess, Schott Glaswerke (Germany)
Rudolf Mueller, Schott Glaswerke (Germany)
Erich W. Rodek, Schott Glaswerke (Germany)
Friedrich B. Siebers, Schott Glaswerke (Germany)

Published in SPIE Proceedings Vol. 1013:
Optical Design Methods, Applications and Large Optics
Andre Masson; Joachim J. Schulte-in-den-Baeumen; Hannfried Zuegge, Editor(s)

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