The active optics system for the Discovery Channel Telescope

The Discovery Channel Telescope (DCT) is a 4.3-meter telescope designed for dual optical configurations, featuring an f/6.1 Ritchey-Chretien prescription with a 0.5° field-of-view, and a corrected f/2.3 prime focus with a 2° field-of-view. The DCT Active Optics System (AOS) maintains collimation and mirror figure to provide seeing limited images across the focal planes and rapid settling times to minimize observing overhead, using a combination of feed-forward and lowbandwidth feedback control via wavefront sensing. Collimation is maintained by tip-tilt-piston control of the M2 assembly and articulating M1 within its cell, taking advantage of the 120 degree-of-freedom support used for figure control. We present an overview of the AOS design and principles of operation, and a summary of progress and results to date.