NSO/Sac Peak continuous-face-plate adaptive mirror

摘要

Abstract: The National Solar Observatory is constructing a continuous-face-plate mirror with 61 actuators. The mirror, which has a clear aperture of 218 mm, features a detachable face plate and replaceable actuators that are servoed to maintain a position measured by capacitors which are within the actuators themselves. The actuators, manufactured by Queensgate Instruments Ltd., are 20 mm diameter and are placed on 32 mm centers. Each has a range of 6.4 $mu for a voltage swing of $POM 175 volts. The servos have a bandwidth of 1 KHz ($MIN@3 db). In order to couple the face plate to the actuators, each actuator has a rare-earth magnet on its end that attracts a steel button cemented to the 3 mm thick glass faceplate. The mirror is a contender for those systems needing a relatively large adaptive mirror with relatively few actuators, for example, to replace the secondary mirror of a Cassegrain telescope. At Sacramento Peak the mirror will be used with the 76 cm aperture Vacuum Tower Telescope to observe small details on the sun. !24