[fitswcs] Polarization codes

[Paddy Leahy]

Hi Steve,

On Thu, 13 Mar 2008, Steve Allen wrote:

> On Thu 2008-03-13T17:19:07 +0000, Paddy Leahy hath writ:
>> Hi Mark et al  (is anyone else reading these posts?)
>
> As with Arnold, yes, but Lick only has one instrument designed to
> measure polarization, and my radio days were 25 years ago.
>
> At the current stage of FITS evolution I find myself questioning the
> creation of any new conventional axis notions for PHDU and IMAGE data
> parallelepipeds.  Unless there is almost uniform agreement on the
> utility of such things it seems to me that it may be better to move
> such data into BINTABLE columns.  In that case each application can
> engineer its own set of descriptions without entangling the whole of
> the FITS community.  This may be a break with tradition for certain
> types of data, but it seems to be used well by the high energy
> community with their visualization and analysis tools.

This is not a proposal that applies only to PHDU and IMAGE extensions. The 
WCS formalism (including the existing coding of stokes parameters) applies 
to generic bintables and (separately) to pixel lists.

>From my perspective it would be a good thing if polarimetrists in 
different fields of astronomy (including high-energy now!) could exchange 
data unambiguously. That is why the IAU and IEEE have gone to the trouble 
of defining the meanings of various polarization parameters. And of course 
ease of data exchange is the main motivation for FITS, wcs, and I suppose 
this mailing list.

regards,

 	Paddy