iraf.net

Hi,
I'm looking for information on how to do the wavelength calibration to a 2-dim image spectrum.
I used to extract the spectrum from a 2-dim image using APALL and then
do the wavelength calibration. It would very useful to do the wavelength calibration to the original 2-dim image in order to extract already calibrated spectra. Does anybody know how to do that or where can I find some info?many thanks

Does "help longslit" help? Assuming you're talking about a single slit spectrum, you should be able to do identify->reidentify->fitcoords->transform to get your 2D spectrum on a linear grid, for example. You might find the following guide useful. http://iraf.noao.edu/iraf/ftp/iraf/docs/spect.ps.ZCheers,James.

James,
thank you very much for your help.
One last point,
since all standards stars I observed are at the same position on the slit
I cannot use the transform routine (anyway there is no noticeable geometrical distortion in the spectra).
I used identify, reidentify and then fitcoords. However, it's not clear for me when do you have your images wavelength calibrated. Do I have to run refspectra and dispcor routines as usual?many thanks again.
charly

[quote:880e89ada8="donzelli"]since all standards stars I observed are at the same position on the slit I cannot use the transform routine (anyway there is no noticeable geometrical distortion in the spectra).[/quote:880e89ada8]
I'm not 100% sure what you're saying, but I believe you can run transform after doing identify and fitcoords on an arc, even if you haven't run identify in the spatial direction.[quote:880e89ada8]I used identify, reidentify and then fitcoords. However, it's not clear for me when do you have your images wavelength calibrated. Do I have to run refspectra and dispcor routines as usual?[/quote:880e89ada8]
The images should have the correct wavelength calibration in the header after you run either transform or dispcor.Cheers,James.

yes, you're right. But it took me a while to realize many thanks again.
charly