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Apparently there is a problem with my dark frames and BIAS frames in module 2) Calibration. The pictures were taken with a CANON EOS 750D (astromodified). In the console output window the warning "we have detected a possible sensor offset issue between the MasterBias and the Masterdark !" appears.
I also suspect that the MasterBias is not subtracted from the Masterdark. The median values of both files are identical.
The file attachment contains the respective FITS header of the MasteBias and of the Masterdark as well as the error message.
Is there an explanation for this?
Stefan B.
Mmm, that is interesting. Maybe the console logs a rounded number while in reality they are slightly different. It only seems to be the case in channel 3. I don't see anything really strange in the fits data either. How do integrations look like and do you see the mention of darks and bias being applied to the light frames when looking on the overview list?
Many thanks for the quick feedback. I quickly integrated 3 lights again. Once calibrated only with BPM and the second time with BPM+MD+MB. The visual difference in the integration file is very small. How can I check that the BIAS has been subtracted from the MD? In the FITS header the MEDIAN value is identical for MD and MB.
In the thread "How to correct a stack/integration for vignetting" ( https://www.astropixelprocessor.com/community/tutorials-workflows/how-to-correct-a-stackintegration-for-vignetting/ ), Mabula described that the ADU of the MD is approximately 0 if the BIAS was subtracted. I am a bit irritated now because the MEDIAN values of my data contradict this.
It looks like the masters are all used, so then it should be substracted yes, it's also a warning and not necessarily a problem, otherwise APP would not continue. Personally I think it's totally fine, but Mabula has the deep know-how that I require in this case so I'll give him a notice. @mabula-admin
ps. never get irritated about data, if I did that I would be very grey by now. 😉
Hello!
Apparently there is a problem with my dark frames and BIAS frames in module 2) Calibration. The pictures were taken with a CANON EOS 750D (astromodified). In the console output window the warning "we have detected a possible sensor offset issue between the MasterBias and the Masterdark !" appears.
I also suspect that the MasterBias is not subtracted from the Masterdark. The median values of both files are identical.
The file attachment contains the respective FITS header of the MasteBias and of the Masterdark as well as the error message.
Is there an explanation for this?Greetings
Stefan B.
Hi @stefan-b & @vincent-mod,
Let me try to clarify what is happening here 😉
Indeed, the console will throw a warning if the median value of the masterdark is lower than the median value of the masterbias. Normally, this would indicate an issue with either gain/iso value or the sensor offset, meaning: perhaps they are not compatible between the masterdark and the masterbias, which would warrent a warning off course.
In this case however, there should be no problem. The newer cmos sensor techonology is reponsible for this to happen on some camera's now. And as you can see, the values are nearly identical so all should be fine.
It seems that in an earlier version of APP, the BIAS was subtracted when creating the MasterDark during calibration. In the current version this is probably no longer the case. I am sure that @mabula-admin has an explanation for the warning message. Many thanks for the help.ps. unfortunately my hair is already grey, more is not possible anymore. But this is not due to APP! 😀 APP is an ingenious program and I like to work with it very much.
Many thanks for the feedback and the extensive explanation. My concerns that something is wrong with the calibration frames or that something is wrong with my camera have fortunately not come true.