Proceedings PaperCast Tenzaloy aluminum optics
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Since the early sixties, cast aluminum optics has held out a promise of low cost, durability, lightweight, ease of manufacture, the possibility of welding together sections to form large optics and a good match of some astronomical programs such as photometry. Needless to say, this rosy future has been fraught with difficulties. Poor short-term stability, sensitivity to temperature, porosity, bimetallic warping, soft optical surface, poor specularity, nickel adhesion problems, poor image quality, and the inability to generate aspherics, have all contributed to the bad name cast aluminum optics has acquired over the years. With the advent of improved aluminum alloys, long-term dimensional stability data, advances in adaptive optics and the need for very large monolithic mirrors with a relatively low handling risk, aluminum optics deserve another look. This paper is a collection of some of the early attempts to build cast aluminum mirrors using the stable alloy, Tenzaloy. The results of those efforts are discussed together with recommendations for future aluminum metal mirror work.