 |
 |
Thanks a lot David, I think that resampling is correct, but just for curiosity which header variables do we eventually have to edit?. (fits header wcs variables are a bit arcane some times) Regards Jaime El Lunes, 25 de Febrero de 2008, David Berry escribió: > On 25/02/2008, David Berry <[log in to unmask]> wrote: > > On 25/02/2008, Jaime Perea <[log in to unmask]> wrote: > > > Ooops, > > > > > > Shame on me, first posting and it was a mistake in the To: field. > > > > > > Anyway, the problem is that SDSS spectra are log lambda spaced > > > instead of lambda. Then a previous scrunch is needed to allow > > > dipso to use those spectra. > > > > Looking at the dipso code, it would have expected it to be able to > > handle log spaced data succesfully. I'd be interested in looking at > > at example SDSS spectrum to see why dipso has problems with the log > > spacing. Can you point me at one? > > The problem is that the standard FITS-WCS headers do indeed describe a > linear coordinate system. They are obviously lying :-) Presumably the > correct WCS information is contained within some of the extra SDSS > headers that are not part of the FITS-WCS standard. It would be > possible of course to edit the headers to include standard FITS-WCS > keywords describing the WCS, in which case DIPSO would corectly pick > up the log axis. But if you are happy for the data to be resampled > onto a linear axis, it is probably easier to scrunch the data using > iraf as Jaime suggests. If you would prefer the data to retain its > logarithmic spacing, then I can let you know how to edit the headers > appropriately. > > David