ESO's New Compact Laser Guide Star Unit Tested

Last night, ESO's Wendelstein laser guide star unit had its first light at the Allg��u Public Observatory in Ottobeuren, Germany. Laser guide stars are artificial stars created high up in the Earth's atmosphere using a laser beam with a power of several watts. The laser, in this case a powerful 20 watt yellow beam (operating at 589 nm) , makes the sodium atoms in a layer 90 kilometres up in the atmosphere glow and so creates an artificial star in the sky that can be observed by a telescope. The adaptive optics equipment can then use measurements of the artificial star to correct for the blurring effect of the atmosphere in the observations.

Here the��Allg��u Public Observatory's 0.6-metre telescope is seen together with the propagating laser beam from the launch telescope further to the right.��