I think Siril can be considered as a photometry compliant software, contrary to what I read here. At least we are doing our best for this. It now has powerful and efficient tools for making light curves.
For this purpose I am trying to integrate the CALSTAT keyword which is apparently used here.
If I understand correctly. Subtracting a bias from an image creates the keyword CALTSTAT = 'B'. If we subtract the Dark: CALTSTAT = 'D'. However, if the dark still contains the bias, should we therefore write CALTSTAT = 'BD'? This would seem logical to me.
I do not see "CALSTAT" in FITS headers of image files taken by AAVSONet and delivered to my VPhot account. And these files show they have been calibrated and are ready for analysis. I do see the following cal related lines in an AAVSONet processed image:
CALDARKdark_10sec_temp-15_bin2_220627.fits and &
ORIGINAAVSOnet pypline: imgproc_py.py
I also do not see "Calstat" listed in https://fits.gsfc.nasa.gov/fits_dictionary.html
I have not used Siril for stacking. One issue I have with many stacking programs is that they strip off much FITS header data during the stacking process that I need to later re-input into the header. Does Siril do that??
I believe I was the person that requested Siril add the CALSTAT keyword. I had been using ASTAP to do my stacking which does that keyword to the FITS header. When I switched to using Siril, I noticed that the "Cal" column in the VPhot images list was no longer colored in, meaning it didn't think the image was calibrated. If I added it manually, it was colored in, so it looked like VPhot was looking for that keyword. I don't know if it is "required" but it is being used by VPhot.
As I look at this more, having DFBS in the CALSTAT field only yields a yellow-filled box in the VPhot images list.
The VPhot manual says this:
Cal: Calibration status
<green box> = Both dark and flat fielded (and possibly bias subtracted)
<yellow box> = Partially calibrated. Hover the mouse over the image to view details (B = bias, D = dark subtracted, F = Flat fielded)
Why is yellow only partially calibrated when it has all the calibrations? Now I'm confused.
I suspect CALSTAT was created by MaximDL.
They define it as:
CALSTAT – indicates calibration state of the image; B indicates bias corrected, D indicates dark corrected, F indicates flat corrected.
It is a string in which VPhot will look for B, D and F, in any order. Seeing all three it will consider the image calibrated.
Note that you can do photometry on an image in VPhot that it does not consider calibrated. If you know that it is, proceed.
Thank you both for…
Thank you both for this answer. So is CALSTAT really necessary for VPhot? Or is it just a hint?
I didn't know it was a MaximDL keyword and I'm working on it because it was requested by a user: https://gitlab.com/free-astro/siril/-/issues/811.
If it's just a hint, maybe it's not worth developing it for Siril.
As a follow-up to George's comment it finds https://cdn.diffractionlimited.com/help/maximdl/FITS_File_Header_Definitions.htm
where CALSTAT is listed in the section "Extension keywords that may be added or read by MaxIm DL, depending on the current equipment and software configuration:".
Also https://github.com/dbenn/photometry_tools/blob/master/modify-fits-header.py where David Benn has posted a python utility that, along with many options, allows you to add CALSTAT if you need to.
It certainly can be added to AAVSOnet with a little work if need be.