Purpose

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  This procedure writes an array of ds9region structures (defined in
  the Beaumont IDL library) into a region file that ds9 undertands

Inputs

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  file: The name of the file to write to.
  regions: An array of ds9reg structures (see ds9reg__define.pro)
  system: The coordinate system to use. Choices are: PHYSICAL, IMAGE,
          FK4, B1950, FK5, J2000, GALACTIC, ECLIPTIC, ICRS

Restrictions

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  Currently, only circle, ellipse, and box regions are supported by
  write_ds9reg.

Modification History

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  2010: Written by Chris Beaumont