Progress of the Laser Guide Star Adaptive Optics at Subaru Telescope

The curvature-wavefront-based adaptive optics (AO) system with a laser guide star is under commissioning at Subaru Telescope. The AO system has been in use since September 2008 using a natural guide star. The testing of laser projection on the sky resumed on February 13, 2009. We have obtained around 0.55 of Strehl ratio in the K band under seeing conditions of 0.4 arcsecond (at K band) using an 8th-magnitude single star. The Strehl ratio was about 0.2 in the K band using a faint guide star around 16th magnitude. Even though the seeing condition was I arcsecond, we obtained an almost diffraction-limited image. The total equivalent magnitude of the laser guide star was estimated at 10.7 magnitude. However, the full width half maximum is around 2 arcseconds under the seeing condition of I arcsecond in K-band.