Review of astronomical adaptive optics systems and plans

Adaptive Optics systems are now working successfully on all major optical telescopes. The sky coverage of these systems is severely limited by the need for bright guide stars, and Laser guide stars have been under development since they were proposed in the 1980s. Laser guide star assisted AO has recently been commissioned at major observatories, and is finally starting to perform well enough, and reliably enough to provide for astrophysical results. The state of the art in astronomical adaptive optics is reviewed here, with emphasis on laser guide star systems. The prospects and challenges of adaptive optics and laser guide stars on the next generation of 'Extremely Large Telescopes' are also examined.