A 40-cm Welded-Segment Lightweight Aluminum Alloy Telescope Mirror

A 40-cm aluminum alloy, nickel plated, mirror has been made by welding together six individually cast segments. The mirror is shown to be stable to within one wave over a temperature of 58 degrees C primarily due to the use of the aluminum alloy Tenzaloy. The weldment as well as the alloy itself are now known to be capable of essentially complete stress relief by annealing. The possibilities of extending the welding technique to considerably larger telescope systems is also discussed.