Posted: Mon Aug 22, 2011 4:41 pm Post subject: Logarithmic wavelength axis: problems with splot?
is IRAF splot supposed to be able to read log-resampled spectra properly? I created some with my own software and found that splot displays what I think are wrong wavelengths. It could be that I understood the FITS WCS papers (especially "Representations of spectral coordinates in FITS") wrongly but I'm not sure...
OK, so I found http://adsabs.harvard.edu/full/1993ASPC...52..467V ("The IRAF/NOAO Spectral World Coordinate Systems") in the meantime and this is apparently still the way the spectral WCS is handled in IRAF. So while my file may be correct, and is actually handled correctly e.g. in SPLAT (and as 2D spectrum also in DS9), it probably cannot be recognized correctly by IRAF tasks until they are rewritten to take into account current WCS standards.
As you surmised, the IRAF spectroscopy system predates the FITS work on spectral coordinate system by decades and updates to the IRAF coordinate systems is, unfortunately, pretty low priority in such a stable system. Logarithm coordinates are supported. In your example you need to
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum