Focus anisoplanatism for 1.2 m telescope laser guide stars in adaptive optics system

A precise simulation the focus anisoplanatism error of Yunnan observatory 1.2 m 61-element laser guide star adaptive optics system, which caused by laser beacon at a finite range travels a different path than does the light from natural star at a infinite range. This error can be eliminated by use of laser guide stars. However, there are two sources of error limit multiple beacon adaptive optical system, beacon position measurement error and conic tilt error. Analysis the two errors when project two to five laser guide stars. The result showed that with the increase of high and number of laser beam, especially the focus anisoplanatism of Na laser guide stars could reduced to 1 rad2.