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      Compute the coordinates of the native pole for a non-polar projection


      For non-polar (cylindrical or conic) projections, the native pole is
      not at the reference point, and WCS_GETPOLE is used to determine the
      position of the native pole. See section 2.4 of the paper
      "Representation of Celestial Coordinates in FITS" by Calabretta
      Greisen (2002, A&A, 395, 1077, also available at
      http://fits.gsfc.nasa.gov/fits_wcs.html Called by WCS_ROTATE

Calling Sequence

      WCS_GETPOLE, crval, lonpole, theta0, alpha_p, delta_p, LATPOLE= ]

Input Parameters

      crval - 2 element vector containing standard system coordinates (the
              longitude and latitude) of the reference point in degrees
      lonpole - native longitude of the celestial North Pole (degrees)
      theta0 - native latitude of the fiducial point

Output Parameters

      alpha_p, delta_p - celestial longitude and latitude of the native pole

Optional Keyword Input Parameters

      LATPOLE - native latitude of the celestial North Pole (degrees)

Revision History

      Written W. Landsman June, 2003
      Fix calculation when theta0 is not 0 or 90 February 2004
      E. Hivon: alpha_p, delta_p consistenly in Radians May 2010

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