http://www.skyandtelescope.com.au 53S LASER STARS
Four laser beams shoot into the sky from Yepun, one of the four giant telescopes that make
up the European Southern Observatory’s Very Large Telescope in Chile. The lasers make
sodium atoms in the upper atmosphere glow, mimicking stars. Sensors monitor these ‘stars’
to determine atmospheric conditions; this information is then applied 1,000 times
per second to the telescope’s deformable secondary mirror, producing sharper images.VISTASR. BACON