Inverted Hindle Mount Reduces Sag of a Large, Precise Mirror

A mount has been devised to satisfy a requirement to suspend a highly precise, flat, circular, low-thermal-expansion glass mirror in a horizontal plane with its reflective side down while keeping the reflective mirror surface flat to within a peak-to-valley depth of less 50 nm. The difficulty of the suspension problem and the significance of the mount conceived as the solution of the problem arise from the large size and weight of the mirror (diameter 101.7 cm, thickness 18.8 cm, mass 385 kg).