Optical design of the Magellan Project 6.5-meter telescope

The Magellan Project 6.5-meter telescope includes focal stations at both Cassegrain and Nasmyth locations. Instruments which use the f/15 infrared secondary will be mounted at the Cassegrain position. The Nasmyth foci will be fed by an f/11 Gregorian secondary. Rapid changes between the Cassegrain and Nasmyth configurations will be accomplished using a flip-tertiary diagonal mirror. The tertiary mirror turret includes a two-element field corrector and atmospheric dispersion compensator for use with the Gregorian secondary. The turret and the tertiary rotate in order to direct the light to one of 5 Gregorian focal stations, as well as to select or to bypass the field corrector/ADC for any focal station. The optical design of the corrector produces a 30 arc-min diameter field. The Gregorian focal ratio has been chosen to accurately match the field curvature of a particular collimator design, which is the first part of an imaging spectrograph with a 30 arc-min field of view. A variety of cameras will be used with this spectrograph. The wide-field camera should cover the entire field of view with a typical rms image diameter of 0.5 arc-sec. The high-resolution camera should cover the central 15 arc-min with a typical rms image diameter of 0.1 arc-sec.