[fitsbits] Coordinate systems for solar image data (fwd)

[Arnold Rots]

PS:
This issue reminded me that there is still something lacking in WCS.
For geocentric equatorial coordinates we have RADESYS to tell us what
our coordinate reference frame is, but for all others we have to infer
it from the name of the individual coordinates.
It would have been convenient to have a single keyword that specifies
the spatial reference frame in use, and that could say 'FK4', 'ICRS',
'HCI', 'MAG', 'HCD', etc.
Then it would also be easy to add planetocentric coordinates, and we
could allow generic CTYPEs like X, Y, Z, LONG, LAT, etc.
What I'm saying is that extending the current standard is laborious
and could have been made easier.

  - Arnold

----- Forwarded message from Arnold Rots -----


There are two other coordinate systems that have been suggested in the
context of the VO: HGC and HCD.  I can't judge whether they are useful.

But I would suggest dropping GEI and HAE since, if I understand it
correctly, they are synonyms for ICRS and Ecliptic, respectively.

Cheers,

  - Arnold

William Thompson wrote:
> There's a new update of the paper Coordinate Systems for Solar Image Data 
> available at
> 
> http://orpheus.nascom.nasa.gov/~thompson/papers/coordinates.pdf
> 
> I've tried to take all of your user comments into account.  Let me know if I 
> missed anything.
> 
> The major changes from the May 13th version are:
> 
> 1.  Corrected the usage of i and j to match the final WCS paper usage.
> 
> 2.  Corrected Table 1, in particular the keyword "iVn_m"
> 
> 3.  Added a section on the use of cylindrical projections for synoptic maps.
> 
> 4.  Added heliocentric inertial (HCI) from Franz and Harper to Table 4.
> 
> Thank you to the people who've reviewed it so far for all your help.
> 
> William Thompson
> 
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> 
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Arnold H. Rots                                Chandra X-ray Science Center
Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
60 Garden Street, MS 67                              fax:  +1 617 495 7356
Cambridge, MA 02138                             arots at head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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----- End of forwarded message from Arnold Rots -----
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Arnold H. Rots                                Chandra X-ray Science Center
Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
60 Garden Street, MS 67                              fax:  +1 617 495 7356
Cambridge, MA 02138                             arots at head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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