For about 20 years SCHOTT has been supplying the glass ceramic ZERODUR, a material with a thermal expansion of virtually zero. ZERODUR is excellently suited for the manufacture of mirror substrates for astronomical telescopes. SCHOTT has accumulated substantial experience in melting and processing of this material. New techniques, such as spin-casting, have been developed by SCHOTT for the manufacture of thin monolithic mirror blanks exceeding 8 m in diameter. These developments resulted in SCHOTT obtaining the order for the manufacture of 4 meniscus shaped shells for the Very Large Telescope of the European Southern Observatory. The corresponding production facilities are currently being erected with the first casting scheduled for the end of 1990. SCHOTT has also performed considerable developmental work in the area of lightweighted ZERODUR mirror substrates which can be fabricated by applying one or a combination of the following techniques: forming of the lightweighted structure during casting, fusion of individual components to a total structure and lightweighting of a massive block by various machining methods.

Date Published: 1 July 1990
PDF: 12 pages
Proc. SPIE 1236, Advanced Technology Optical Telescopes IV, (1 July 1990); doi: 10.1117/12.19242

Published in SPIE Proceedings Vol. 1236:
Advanced Technology Optical Telescopes IV
Lawrence D. Barr, Editor(s)