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Adaptive optics allows the theoretical limit of angular resolution
to be achieved from a large telescope, despite the presence of
turbulence. Thus an eight meter class telescope, such as one of the
four in the Very Large Telescope operated by ESO in Chile, will in
future be routinely capable of an angular resolution of almost 0.01
arcsec, compared tot he present resolution of about 0.5 arcsec for
conventional imaging in good condition. All the world's major
telescopes either have adaptive optics or are in the process of
building AO systems. It turns out that a reasonable fraction of the
sky can be observed using adaptive optics, with moderately good
imaging quality, provided imaging in done in the near IR. To move
out of the near IR, with its relatively poor angular resolution,
astronomers need a laser guide star. There is a layer of Na atoms
at approximately 90 km altitude that can be excited by a laser to
produce such a source, or Rayleigh scattering can be employed lower
in the atmosphere. But the production and use of laser guide stars
is not trivial, and the key issues determining their successful
implementation are discussed here, including the physics of the Na
atom, the cone effect, tilt determination, sky coverage, and
numerous potential astronomical applications.
Adaptive optics allows the theoretical limit of angular resolution
to be achieved from a large telescope, despite the presence of
turbulence. Thus an eight meter class telescope, such as one of the
four in the Very Large Telescope operated by ESO in Chile, will in
future be routinely capable of an angular resolution of almost 0.01
arcsec, compared tot he present resolution of about 0.5 arcsec for
conventional imaging in good condition. All the world's major
telescopes either have adaptive optics or are in the process of
building AO systems. It turns out that a reasonable fraction of the
sky can be observed using adaptive optics, with moderately good
imaging quality, provided imaging in done in the near IR. To move
out of the near IR, with its relatively poor angular resolution,
astronomers need a laser guide star. There is a layer of Na atoms
at approximately 90 km altitude that can be excited by a laser to
produce such a source, or Rayleigh scattering can be employed lower
in the atmosphere. But the production and use of laser guide stars
is not trivial, and the key issues determining their successful
implementation are discussed here, including the physics of the Na
atom, the cone effect, tilt determination, sky coverage, and
numerous potential astronomical applications.
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