PHOTOS: Cosmic Hotshots from Keck Observatory
In the case of the VLT's new adaptive optics system, four 22 Watt laser beams shoot out of the dome. On encountering sodium atoms in the high atmosphere, these atoms glow, creating fake stars. These points of light at then used by the telescope to directly measure the amount of turbulence in the upper atmosphere. This information is then fed back into automated systems on the telescope to manipulate the telescope's primary mirror, compensating for the atmospheric interference. By canceling out atmospheric interference, the observatory will get a crisper and more precise view of distant stars and galaxies.
While the science is cool, the view is out of this world: