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APP apparently doesn't calibrate with master dark for OIII algorithm?  

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(@mseningmail-com)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
February 3, 2021 10:19  

I have some data from ZWO294MC Pro camera used with L/H/S/O filters. Each filter's files were processed with darks, bias and flat frames.
This is a colour camera, so I'm using OIII/Ha/SII debayering algorithms.
For Ha and SII as well as for L filter, the amp glow is 95-99% eliminated by the dark frames, but for OIII the amp glow is horrendous.

Either darks are not applied to OIII algorithm or it's amplifying the amp glow somehow, or I'm missing something.

image

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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1113
February 3, 2021 11:28  

@mseningmail-com Can you tell a bit more about the lights and the darks? What exposure time did you use for them? And just to be on the safe side, can you confirm that they were all taken at the same temperature, gain and offset? What software did you use to take them?


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(@mseningmail-com)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
February 3, 2021 21:00  

I originally shot the dark frames on the same night as I took the lights back in October in the local mountains. The camera was cooled to -10C, in case I needed to re-shoot darks later: -20C would not be achievable from my home because it gets hot here most of the year.

All exposures were at Bin1, G=200, Temp=-10C and Exp=120s. AFAIK the offset is built into the camera and FITS header says it's always 30.
I had to reshoot darks several times until I got reasonable results in most filters. But OIII is the worst.

They were taken with ZWO ASIAIR and ZWO ASI294MC Pro.

The latest Dark FITS header:

SIMPLE = T / file does conform to FITS standard
BITPIX = 16 / number of bits per data pixel
NAXIS = 2 / number of data axes
NAXIS1 = 4144 / length of data axis 1
NAXIS2 = 2822 / length of data axis 2
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
BZERO = 32768 / offset data range to that of unsigned short
BSCALE = 1 / default scaling factor
CREATOR = 'ZWO ASIAIR' / Capture software
OFFSET = 30 / camera offset
XORGSUBF= 0 / Subframe X position in binned pixels
YORGSUBF= 0 / Subframe Y position in binned pixels
FOCALLEN= 247 / Focal length of telescope in mm
EGAIN = 0.398999989032745 / Electronic gain in e-/ADU
XBINNING= 1 / Camera X Bin
YBINNING= 1 / Camera Y Bin
CCDXBIN = 1 / Camera X Bin
CCDYBIN = 1 / Camera Y Bin
XPIXSZ = 4.63000011444092 / pixel size in microns (with binning)
YPIXSZ = 4.63000011444092 / pixel size in microns (with binning)
IMAGETYP= 'Dark ' / Type of image
EXPOSURE= 120. / Exposure time in seconds
EXPTIME = 120. / Exposure time in seconds
CCD-TEMP= -10. / sensor temperature in C
DATE-OBS= '2021-02-03T04:21:12.164' / Image created time
INSTRUME= 'ZWO ASI294MC Pro' / Camera model
BAYERPAT= 'RGGB ' / Bayer pattern
GAIN = 200 / Gain Value

The sample Light FITS header:

SIMPLE = T / file does conform to FITS standard
BITPIX = 16 / number of bits per data pixel
NAXIS = 2 / number of data axes
NAXIS1 = 4144 / length of data axis 1
NAXIS2 = 2822 / length of data axis 2
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
BZERO = 32768 / offset data range to that of unsigned short
BSCALE = 1 / default scaling factor
CREATOR = 'ZWO ASIAIR' / Capture software
OFFSET = 30 / camera offset
XORGSUBF= 0 / Subframe X position in binned pixels
YORGSUBF= 0 / Subframe Y position in binned pixels
FOCALLEN= 247 / Focal length of telescope in mm
EGAIN = 0.398999989032745 / Electronic gain in e-/ADU
XBINNING= 1 / Camera X Bin
YBINNING= 1 / Camera Y Bin
CCDXBIN = 1 / Camera X Bin
CCDYBIN = 1 / Camera Y Bin
XPIXSZ = 4.63000011444092 / pixel size in microns (with binning)
YPIXSZ = 4.63000011444092 / pixel size in microns (with binning)
IMAGETYP= 'Light ' / Type of image
EXPOSURE= 120. / Exposure time in seconds
EXPTIME = 120. / Exposure time in seconds
CCD-TEMP= -10. / sensor temperature in C
RA = 10.943715 / Object Right Ascension in degrees
DEC = 41.3451 / Object Declination in degrees
DATE-OBS= '2020-10-19T09:21:39.154' / Image created time
FILTER = 'O ' / Filter used when taking image
INSTRUME= 'ZWO ASI294MC Pro' / Camera model
BAYERPAT= 'RGGB ' / Bayer pattern
GAIN = 200 / Gain Value
TELESCOP= 'EQMod Mount' / Telescope name

 


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(@mseningmail-com)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
February 3, 2021 21:02  

...I can still see some amp glow in Ha and SII stacks, but RGB (OSC) looks relatively good - I can crop what's left.


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(@mseningmail-com)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
February 3, 2021 21:08  

I don't know if it's related, but I'm still on Version 1.082. I reported a bug previously where "extract Ha" and "extract OIII" algorithms were resulting in the same image and also if any drizzling were used it would leave black pixels in there. I heard it's fixed in 1.083 beta3, so please let me know if I should just wait for the new version to try stacking it again?
Just to be clear, these images were shot with ZWO ASI294MC Pro, which is an OSC camera, and for narrowband filter images I selected Ha/OIII/SII debayering algos as opposed to "Exctract ___" algos.


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