On-sky wide-field adaptive optics correction using multiple laser guide stars at the MMT

We describe results from the first astronomical adaptive optics (AO) system to use multiple laser guide stars, located at the 6.5 m MMT telescope in Arizona. Its initial operational mode, ground-layer adaptive optics (GLAO), provides uniform stellar wave front correction within the 2' diameter laser beacon constellation, reducing the stellar image widths by as much as 53%, from 0."70 to 0."33 at λ = 2.14 μm. GLAO is achieved by applying a correction to the telescope's adaptive secondary mirror that is an average of wave front measurements from five laser beacons supplemented with image motion from a faint stellar source. Optimization of the AO system in subsequent commissioning runs will further improve correction performance where it is predicted to deliver 0."1-0."2 resolution in the near-infrared during a majority of seeing conditions