Stressed-lap Polishing of Large, Highly Aspheric Primary Mirrors

Abstract

Stressed-lap polishing has been used to complete three fast borosilicate honeycomb-sandwich mirrors. The 1.8-m f/1 primary mirror for the Lennon Telescope being built by the Vatican Observatory and the University of Arizona has been figured to an accuracy of 17 nm rms surface error, the 3.5-m f/1.5 primary mirror for the Starfire Optical Range of the U. S. Air Force Phillips Laboratory to 21 nm rms, and the 3.5-m f/1.75 primary mirror for the Astrophysical Research Consortium to 19 nm rms. The 3.5-m mirrors were figured in a new polishing facility, using a computer-controlled polishing machine and vibration-isolated test tower both sized for 8-m mirrors.