Adaptive optics with a Laser For Astronomy

A short 24-frame video showing ALFA's laser guide star on the wavefront sensor during May 1999. The single lenslet was used, and the sampling rate was 100 Hz so the movie corresponds to only 1/4 sec of actual time.

LGS video

The jitter is entirely atmospheric, and arises because the laser beam propogates upward along a different path to the downward propogation of the light from sodium fluorescence. Thus the LGS is seen to have about twice as much jitter as a normal star. The pixel scale here is around 0.43'', so the image motion is on the order of 1-1.5arcsec.

A single spot is useful when carrying out experiments on the laser beam, such as measuring the effect of polarisation on the spot brightness.