Spectrum - Crop & PixInSight

[cbrunfranc]

Hello

I'm starting to do some spectrometry.
I'm taking picture with a EOS CANON 40D. I want to make calibration/registration/stacking with PixInSight.

I want to accelerate the processing.
As the "meaningfull part" of the picture is very little (only order 0 and order 1 of the spectrum), I want to  crop the picture before to make any treatment.

Is there any issue with this - working with fits pictures and not anymore RAW picture  ?
or "crop" must be done after all treatment to work with RAW picture ?

Bonus question : is it possible to align spectrum + star with staralign feature (or there is more "relevant" feature for this in PI) ?

Thanks for your advice/sharing your experience

Christophe -BF-

[apricot]

Bonjour Christophe,
Yes it is possible to calibrate and registrate and stack your spectra in PI. Calibration (bias dark and removal of hot pixels and cosmics) is done just as for standard images. For registration, Pi can work with the zero order images of the stars (assuming your working on spectra obtained with a star analyzer) but I could not find a way to register the spectra only. Stacking can be done as usual. And yes, you can batch crop your fits images to reduce the size of the images and work only on the spectrum and the zero order star image (and even registrate the spectra while doing so).
Just make sure to keep the spectra images linear, with no treatment at all, before analysis in e.g. VSpec.
Hope this helps,
Jean-Phi / apricot

[cbrunfranc]

Thanks for your clear answer !
I will try to follow your advice.
Regards
Christophe -BF-