Very Large Telescope The Very Large Telescope array (VLT) is the
flagship facility for European ground-based astronomy at the
beginning of the third Millennium. It is the world's most
advanced optical instrument, consisting of four Unit Telescopes
with main mirrors of 8.2m diameter and four movable 1.8m
diameter Auxiliary Telescopes. The telescopes can work together,
to form a giant ‘interferometer’, the ESO Very Large Telescope
Interferometer, allowing astronomers to see details up to 25
times finer than with the individual telescopes. The light beams
are combined in the VLTI using a complex system of mirrors in
underground tunnels where the light paths must be kept equal to
distances less than 1/1000 mm over a hundred metres. With this
kind of precision the VLTI can reconstruct images with an
angular resolution of milliarcseconds, equivalent to
distinguishing the two headlights of a car at the distance of
the Moon. The 8.2m diameter Unit Telescopes can also be used
individually. With one such telescope, ima