oh come on, if you don't understand this your just fick
The 4LGSF is part of a next-generation
adaptive optics system, the Adaptive Optics Facility (AOF), that will make the VLT’s 4th Unit Telescope Yepun a fully adaptive telescope in 2013. Composed of four powerful 20-watt lasers, the 4LGSF will help the VLT correct the image distortion caused by turbulence in the air.
Telescopes usually collect light coming from the sky and focus it into an instrument. However, the new components send light in the opposite direction. These “launchers”, are used to project the lasers into the sky to create brilliant points of light. The laser beams excite a layer of sodium atoms at an altitude of 90 kilometres in the atmosphere and make them glow. These glowing spots act as an artificial guide star which can be positioned at will in the sky, so astronomers are not restricted to observations close to a sufficiently bright natural guide star.
With four such artificial stars, the 4LGSF will be able to dramatically improve sharpness [1] across the wide field of the VLT’s near-infrared camera HAWK-I. Single laser systems, although providing excellent image quality, are restricted to much smaller fields of view
The first such system on the VLT was installed just over ten years ago. In early 2006, the technology was improved with
the first use of a laser guide star at the VLT.
basic stuff right
https://www.tno.nl/vlt4lgsf/
