[fitswcs] unambiguous rotation angle

[Peter Bunclark]

On Wed, 16 Jan 2002, Steve Allen wrote:
> (This ignores the much larger terrestrial effect of differential
> refraction.  All of this, by the way, might be significantly
> clarified if concatenation of WCSs were allowed so that each step
> implemented a particular bit of physics or optics.)
>
In other words, implement a model rather that a fit?

Regarding earlier comments about `lack of discussion' which seemed to
start this recent storm of discussion, some of us at least have been
keeping quiet in the hope that discussion stops and publication starts.
For example, I would probably prefer CD over PC, but frankly I don't care
as long as we get told exactly what we should be doing.

Pete.