Image motion correction using accelerometers at the MMTObservatory

摘要

At the MMT Observatory, the adaptive secondary system is producing well corrected images using natural guide stars. Shortly after the system came online, however, it was found that vibrations in the telescope structure were limiting the Strehl of the corrected image. The worst of these vibrations are at 19 Hz, which puts them just outside of the system correction bandwidth. The laser guide star system at the MMT is also impacted by a different vibration mode at 14 Hz that affects the pointing of the laser beacon on the sky. To correct these errors, accelerometers were installed on the secondary mirror to measure its motion. The measured motion was then used to generate a feed-forward correction term which has already been proven in on-sky testing to work for the LGS case. The NGS case is more difficult and attempts to correct image motion have failed due to excessive feedback.