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I have been experimenting (again) with Demetra and have been trying to incorporate a cosmic ray removal routine. I have wrapped the 'industry standard' Laplacian edge detection-based algorithm (LAcosmic) in a way suitable for use with Demtra. It works on the preprocessed files named _Object_P. I (ho...

So I have determined that, for 2x2 binned images, there is no setting of the cosmic ray threshold that allows eradication of cosmic rays without compromising the spectrum itslelf. I suspect that (for a well-focussed star with no DEC drift) the vertical intensity gradient across pixels is comparable ...

Hi David Thanks... I realised after I posted that cosmetic information couldn't be scaled because it is just a list of pixels - all intensity information has been lost. I can also see that using the cosmetic file derived form the unscaled-longest-exposure-dark is OK, as although it will be somewhat ...

Many thanks Robin

I'm glad I know what the @map files are for now! I'll experiment a bit and see...

Kevin

In my search for a solution to my 'strange artefact' problem, about which posed recently, I started to think about the cosmetic file... I understand that the dark is scaled automatically for the exposure, but what about the cosmetic file? Do you just make one for the 'reference dark' (with longest e...

I think I may have cracked it... Having tried many things, I finally came to try turning the cosmic ray filter off... This eradicated the artefact. I can see that very bright portions of a spectrum can look like a cosmic ray strike. I think I am just going to stop using this filter from now on... I ...

I came to do the routine processing of a reference star for an Alpy target and saw something strange in the final profile. Thus, there were several well-defined, and equally-spaced 'notches' therein. I finally tracked the source of this artefact to the processing of a singe sub-exposure (1 out of 5)...

I understand from David Boyd that there was a change in policy over flats processing between the versions I am using that almost certainly accounts for the behaviour I am seeing.
Phew! (and thanks again David)

... Its actually not just a scaling, as the new (v6) spectra are still normalised in the desired range . So they now have a different shape being more 'peaked'..
??

Kevin

I have just been processing some Alpy spectra in version 6.1.1 and noticed that the instrument response (IR) I obtained using a MILES star was quite different from anything I used to have. I tracked this down to the fact that the un-corrected spectrum has a much larger amplitude than before (direct ...