[fitswcs] Polarization codes

[Perry Greenfield]

On Mar 28, 2008, at 2:19 AM, Mark Calabretta wrote:

>
> On Thu 2008/03/27 21:53:37 MDT, Doug Tody wrote
>
>> parts of the WCS concept and technology were developed independently
>> in IRAF, way back in the eighties, and with great reluctance were
>
> Original versions of G&C (it started as a single paper) used the CDi_j
> variant of the CD00i00j matrix proposed by Hanisch & Wells (1988)  
> which
> came from the NASA-sponsored meeting held in Charlotesville in Jan/ 
> 1988.
> Isn't that where IRAF got the CD matrix?
>
> However, we are obliged to you for convincing us to preserve CDELTn.
> This followed a discussion between you and Eric at the AAS meeting in
> Berkeley in 1993, I have the email from Eric detailing your reasons if
> you want to see it.  Consequently we reverted to CDELTi + matrix.
> Initially we were going to call it CDi_j with the current meaning of
> PCi_j but there were objections regarding prior conflicting usage in
> IRAF so Eric changed the name.  Your original email accepting this
> solution is appended.
>
>> later allowed to influence the development of the actual WCS  
>> standard,
>> which has always been tightly controlled by G&C.
>
> Later you insisted that we must revert to the CDi_j matrix.  I don't
> recall that you ever provided a reason, I believe it was simply  
> because
> it was the way IRAF did it.  That is what we resisted, for the reasons
> originally espoused by you in 1993, and for compelling reasons that
> emerged subsequently, c.f. Sect. 2.1.2 of Paper I.
>

I haven't been following this whole thread so I may be taking this  
out of context. My recollection is that the CD convention was already  
in use for HST images and thus there was a strong desire not to redo  
that convention or the software that supported it. I don't think it  
was just Doug that insisted that it not be dispensed with or its  
meaning changed. Indeed, I thought it was STScI that was most  
insistent on that point. If that was the case, I'd be very surprised  
that the reason wasn't very explicit at the time. But I was not  
really involved in the issue at the time if I recall correctly. Bob  
can correct me if I got this wrong.

Perry