The Optical Design of the 40-in. Telescope and of the Irenee DuPont Telescope at Las Campanas Observatory, Chile.

The optical specifications of two astronomical telescopes designed to permit wide-field photography with critical definition are presented and compared. The 40-in. (1.016-m) and DuPont 100-in. (2.54-m) telescopes use modifications of the Ritchey-Chretién design with Gascoigne correctors. By avoiding the need for field flatteners through choice of mirrors yielding zero Petzval sum (40-in. telescope) or bending of photographic plates to a moderate field curvature (100-in. telescope), it was possible to achieve monochromatic images of ? to (1/4) sec of arc over fields of 3 degrees and 2.1 degrees , respectively.