In order to keep astronomical images steady, a natural star nearby in the sky must be monitored in order that the motion of the laser guide star can be subtracted using a tip-tilt mirror. This star can be positioned anywhere the telescope desires to point, opening up much greater amounts of the sky to adaptive optics.īecause the laser beam is deflected by astronomical seeing on the way up, the returning laser light does not move around in the sky as astronomical sources do. Light from the beam is reflected by components in the upper atmosphere back into the telescope. Instead, one can create an artificial guide star by shining a laser into the atmosphere. Natural stars can serve as point sources for this purpose, but sufficiently bright stars are not available in all parts of the sky, which greatly limits the usefulness of natural guide star adaptive optics.
Adaptive optics (AO) systems require a wavefront reference source of light called a guide star. LGS used at the European Southern ObservatoryĪ laser guide star is an artificial star image created for use in astronomical adaptive optics systems, which are employed in large telescopes in order to correct atmospheric distortion of light (called astronomical seeing).
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