Representing Celestial Coordinate Systems - 10

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What aspects of the WCS proposal are specific to FITS, and what would we do differently if starting again from scratch (e.g. XML)?

• All angles in degrees?
  
  OK, suits astronomy and software.



• Left-handed (X, Y) coordinates?
  
  Required for but can be very confusing.



• Define the Euler angles by specifying the celestial coordinates at the reference point (CRVALi)?
  
  Also necessary for first-order behaviour but complicates non-zenithal projections.



• Require at all?
  
  Yes, it ties the celestial coordinate system to a particular point in the image.



• Encode the algorithm type in CTYPEi?
  
  No, too restrictive.