Performance of the active M1 cell for the 2.1-m telescope of the Observatorio Astronomico Nacional de Mexico

摘要

Abstract: Optical testing of the 2.1-m telescope in San PedroMartir, Observatorio Astronomico Nacional de Mexico, bythe methods of wavefront curvature sensing andbi-Ronchi analysis, has shown that the telescopesuffered of large amounts of astigmatism. We identifiedthese as due to improper primary mirror support anddeveloped an active control system to correct for it.The number and position of the actuators were decidedin accordance to the flexural modes that needed to becorrected, resulting in a system of 18 pressurecontrolled pneumatic actuators, with an outer loop thatverifies the load at three hard points. A PID algorithmand matrix inversion are fundamental parts of thisouter loop, that guarantees that the M1 mirror istilted as a rigid body to maintain it properly aligned.The successful performance of the system to correct loworder aberrations is reported.!5