wavelength calibration
donzelli wrote on May 31, 2010
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
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
James Turner wrote on May 31, 2010
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.Z
Cheers,
James.
http://iraf.noao.edu/iraf/ftp/iraf/docs/spect.ps.Z
Cheers,
James.
donzelli wrote on May 31, 2010
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
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
James Turner wrote on May 31, 2010
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).
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.
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?
The images should have the correct wavelength calibration in the header after you run either transform or dispcor.
Cheers,
James.
donzelli wrote on May 31, 2010
yes, you're right. But it took me a while to realize :)
many thanks again.
charly
many thanks again.
charly
Last post on May 31, 2010