The 152-cm telescope of the Cerro Tololo Inter-American Observatory in Chile is to be made to a design producing images that are free of the usual Ritchey-Chrétien astigmatism. A 38-cm diam fused-quartz correcting plate is used to give a field diameter of 1.°5, over which images are less than 0.5 see of arc in diameter.
D. H. Schulte, "Anastigmatic Cassegrain Type Telescope," Appl. Opt. 5, 309-311 (1966)