[fitsbits] [Fwd: PV index perhaps wrong in version 3.0]

[Eric Greisen]

William Pence wrote:
> The question below regarding WCS keyword usage was sent to the FITS
> support office.  Is Table 8.1 in the FITS Standand incorrect?  (See
> http://fits.gsfc.nasa.gov/fits_standard.html ).
> Should it state that LONPOLEa and LATPOLEa
> are associated with PVi_3a and PVi_4a instead of PVi_1a and PVi_2a?
> 
> Bill
> 
> -------- Original Message --------
> Subject: PV index perhaps wrong in version 3.0
> Date: Mon, 08 Sep 2008 14:35:34 +0200
> 
> L.S.,
> 
> Table 8.1 section 8, page 74 lists for the native longitude and latitude
> of the celestial pole the keywords LONPOLEa= and LATPOLEa= which,
> according to the table is equivalent to PVi_1a and PVi_2a.
> However, in the same table these keywords were previously attached to
> the fiducial point. Also Calabretta and Greisen use PVi_3a and PVi_4a in
> their article 'Representations of celestial coordinates in FITS'.
> Please can you inform me about what is right (i.e. standard FITS) in
> this case?
> 

I believe that the user is correct and _3 and _4 should be used.  I was 
hoping Mark Calabretta would confirm this.

Eric