AST472223

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AST4722/23

• Astronomical Seeing

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A display of seeing

• This movie is composed of 42 frames, each image a
  0.5 second exposure of a star through a green
  filter. The seeing illustrated here is actually
  rather good.

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Adaptive Optics

• (see http//op.ph.ic.ac.uk/ao/overview.html )

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Laser Guide Star

• Two methods
• Rayleigh backscatter of laser at an altitude of
  15-20km
• A laser tuned to the Na-line ( backscatter from a
  layer of sodium at an altitude of around 90km)
• The light from the beacon does not travel through
  exactly the same path as the light from the
  (distant) astronomical object under study.
• At any instant the wavefront distortion measured
  using the laser beacon will differ from the true
  wavefront

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Questions and/or Comments? Let me know at
oliver_at_astro.ufl.edu or visit http//www.astro.uf
l.edu/oliver/