All,
Just got this from Mark Calabretta, regarding the handling of units by
WCSLIB:
"However, although space is reserved for it in the wcsprm struct, WCSLIB
cannot currently parse CUNITia and assumes SI/deg (without checking). I
imagine this is probably true for most other FITS WCS software. I would
advise against writing anything but SI/deg for now."
Ooooo!!! AST does parse and use CUNITia correctly (i.e. in accordance with
FITS-WCS paper 1), both when reading and writing FITS headers. The up-shot
is that you need to beware of using AST to produce FITS-WCS frequency axes
in units of MHz, km/s, etc instead of Hz and m/s if you intend the FITS
file to be read by some other WCSLIB-based software.
David
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