Adaptive Optics – Correcting the Image
For an example of the image improvements that adaptive optics provides check out the view on this page. A “calibration” of sorts must be made to tune the adaptive optics system. If there is a guide star in the sky near the area of interest then that can be used. If not, most telescopes shoot a laser into the sky that causes a sodium gas to glow about 60 miles out. The telescope focuses on this glow and calibrates the system for it.