spectro-aras.com

Hi
I've noticed a few peaks in my spectra which I've traced to background light. I can remove them but need to reduce the sky removal lines until they are almost touching the spectrum and I'm wondering if there is a better way of doing it? My binning zone is about 5 pixels high at the moment to enable this which as I have to initially rotate the spectrum slightly is not really practical unless that is the only way. I would be interested to hear how others remove this background light 'noise' with ISIS please!
Thanks
Steve

Hi Steve,

Provided you get your geometric corrections right, particularly smile/slant, the background lines should cancel independent of where you set the skybackground zones. Attached is an extreme example from my recent QSO measurement showing the ISIS binning zones and geometric correction settings used and the resulting processed spectrum images with and without sky background subtraction

Robin

Thanks yet again Robin
I wasn`t aware that a bright line above and below would cancel each other out!. I did notice I used a 400sec light but with a 300sec dark which might make a difference.
I also notice that since updating ISIS to 5.4.1 my spectra is now in colour?? This is one of TCrb! regards
Steve

SteveCuthbert wrote: I also notice that since updating ISIS to 5.4.1 my spectra is now in colour?? This is one of TCrb!

Molecular lines showing nicely there in T CrB
The colour comes from "settings" "rainbow". I've not used it myself but I presume you have to enter the extreme left and right wavelengths in the image to get the colours approx right (eg is the bright sky line in the red actually the Na D line?)

Cheers
Robin

Hi Robin
I didn`t even notice there was a `rainbow` setting in ISIS , it must default to `rainbow` in 5.4.1.as I didn`t select it! Not sure if the colouring is correct when ISIS finishes its calibrating?.
Best
Steve

See "Settings" tab and left lower corner. Note "Display" area and unselect Rainbow option.

Christian