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We have designed and installed a new set of actuators for the suspension of the primary mirror of the 2.1-m telescope at San Pedro Mártir. This active optics system has allowed us to correct low-order aberrations identified by several wave-front analysis techniques.

The Telescopio San Pedro Mártir project intends to construct a 6.5m telescope to be installed at the Observatorio Astronómico Nacional in the Sierra San Pedro Mártir in northern Baja California, Mexico. The project is an association of Mexican institutions, lead by the Instituto Nacional de Astrofísica,Óptica y Electrónica and the Instituto de Astronomía at the Universidad Nacional Autónoma de México, in partnership with the Smithsonian Astrophysical Observatory and the University of Arizona's Department of Astronomy and Steward Observatory. The project is currently in the planning and design stage. Once completed, the partners plan to operate the MMT and TSPM as a binational astrophysical observatory.

Optical testing of the 2.1-rn telescope in San Pedro Mártir, Observatorio Astronórnico Nacional de Mexico, by the methods of wavefront curvature sensing and bi-Ronchi analysis, has shown that the telescope suffered of large amounts of astigmatism. We identified these as due to improper primary mirror support and developed an active control system to correct for it. The number and position of the actuators were decided in accordance to the flexural modes that needed to be corrected, resulting in a system of 18 pressure controlled pneumatic actuators, with an outer loop that verifies the load at three hard points. A PID algorithm and matrix inversion are fundamental parts of this outer loop, that guarantees that the Ml mirror is tilted as a rigid body to maintain it properly aligned. The successful performance of the system to correct low order aberrations is reported.