Well, not specifically about dual sideband data but about radio spectral
line data in general. The best description of the relevant keywords
that I've found is in the NRAO AIPS++ documentation at
http://aips2.nrao.edu/docs/notes/236/node14.html. However, the
definitions are not entirely unambiguous. That's why I posted my
interpretation, to see if anyone disagreed.

Regards

Tom

David Berry wrote:
It looks like Tom's query was about dual sideband data, which is not
covered by paper III. OBSFREQ, etc, are not in the standard. There are
probably various different schemes in use out there. For instance JCMT
and CLASS software use a system based on a keyword called IMAGFREQ,
which holds the image sideband rest frequency (with RESTFREQ holding
the observed sideband rest frequency).

David


2009/5/5 LC's No-Spam Newsreading account :

On Mon, 4 May 2009, Tom Kuiper wrote:


I'd like to get it clear in my mind what the various frequency
definitions are. Is the following right? If there is a place where
all this is clearly laid ou, please refer me to that.

Not a spectral WCS expert, but the standard and official references
are :

- http://fits.gsfc.nasa.gov/fits_standard.html
the latest release of the FITS standard, in particular chapter 8

- the full WCS paper III, either as published or
http://www.atnf.csiro.au/people/mcalabre/WCS/scs.pdf

(the other WCS papers are all listed in
http://www.atnf.csiro.au/people/mcalabre/WCS/index.html

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