Trouble processing OSC images of M 20

Check your debayer pattern. If I don't force GRBG my colors are all off too

Posted by: gdwats@comcast.net

Check your debayer pattern. If I don't force GRBG my colors are all off too

Thank you sir!! Mistakenly I had set the bebayer to RGGB!!! No wonder it was so green!! LOL

Glad I could help  👍 

So I reran my integration this time using the GRBG setting for deBayer. I got a different result, but one I still can not tease the colors I normally see in photos of M 20. I'm super happy with the nice round stars. This image has been through "remove light pollution, Neutralize Background, and Star color Calibration.

I've tried changing the parameters in star color calibration with no success. Also in HSL selective color. Nothing seems to work.

Again try as I may I can not tease out the "correct" colors. Not in APP or Photoshop CC.

SMH!!

Thom

Hi Thom @thompeters & Greg @gregwrca,

I agree, after having set the correct Bayer pattern, the result still looks odd.

Perhaps I need to have a look at a single exposure of the asi1600MC. Can you send me 1 or a couple of exposures, so I can have a look? Perhaps send me the integration result that you have as well.

So only a IR/UV cut fitler was used?

Kind regards,

Mabula

Ok Mabula! Remind me on how to send you the files??

yes, only the UV/IR cut filter used. 

Thom

OK Mabula - I found the old message so I'm sending the files by wetransfer.com to your support email (support@astropixelprocessor.com).

Thanks Thom

Hi Thom @thompeters,

Thanks for the files, I wll report back my findings as soon as possible 😉

Mabula

Just wondering if you'd had time to look at the files yet Mabula?

Hi Thom @thompeters,

Not yet, apologies for the delay.

Can you please send me the data again by wetransfer.com ? (Download has expired)

I will then download it immediately, I promise 😉

Mabula

I know you’re super busy, no problem!!

Dear Thom @thompeters,

I have checked your data. Something odd is happening with the captures of SGP.

The 2 images that you sent me requires different CFA patterns.

M 20 Trifed Nebula_120sec_gain_NA_offset_NA_Deg NA__frame13.fit

FITS header:

FITS HDUs: 1
HDU1 - SIMPLE = T / file does conform to FITS standard
HDU1 - BITPIX = 16 / number of bits per data pixel
HDU1 - NAXIS = 2 / number of data axes
HDU1 - NAXIS1 = 4656 / length of data axis 1
HDU1 - NAXIS2 = 3520 / length of data axis 2
HDU1 - BZERO = 32768 / offset and data range to that of unsigned short
HDU1 - BSCALE = 1 / default scaling factor
HDU1 - CRPIX1 = 2328 / reference spectrum pixel coordinate for axis 1
HDU1 - CRPIX2 = 1760 / reference spectrum pixel coordinate for axis 2
HDU1 - CTYPE1 = 'RA---TAN' / standard system and projection
HDU1 - CTYPE2 = 'DEC--TAN' / standard system and projection
HDU1 - OBJECT = 'M 20 Trifed Nebula' / Object name
HDU1 - DATE-LOC= '2018-08-04T01:01:26' / Local observation date
HDU1 - DATE-OBS= '2018-08-04T05:01:26' / UTC observation date
HDU1 - IMAGETYP= 'LIGHT ' / Type of frame
HDU1 - CREATOR = 'Sequence Generator Pro v3.0.2.91' / Capture software
HDU1 - PROFILE = 'ASI1600 & AVX' / SGPro profile name
HDU1 - INSTRUME= 'ZWO ASI1600MC' / Instrument name
HDU1 - EXPOSURE= 120 / Exposure time in seconds
HDU1 - XBINNING= 1 / Camera X Bin
HDU1 - CCDXBIN = 1 / Camera X Bin
HDU1 - YBINNING= 1 / Camera Y Bin
HDU1 - CCDYBIN = 1 / Camera Y Bin
HDU1 - TELESCOP= 'Celestron Telescope Driver' / Telescope name
HDU1 - RA = 270.618711205562 / Object Right Ascension in degrees
HDU1 - DEC = -22.9920816105201 / Object Declination in degrees
HDU1 - CRVAL1 = 270.618711205562 / RA at image center in degrees
HDU1 - CRVAL2 = -22.9920816105201 / DEC at image center in degrees
HDU1 - OBJCTRA = '18 02 28.491' / Object Right Ascension in hms
HDU1 - OBJCTDEC= '-22 59 31.494' / Object Declination in degrees
HDU1 - AIRMASS = 3.1485563844206 / Average airmass
HDU1 - OBJCTALT= 18.4023251531017 / Altitude of the object
HDU1 - CENTALT = 18.4023251531017 / Altitude of the object
HDU1 - ANGLE = 0 / Image angle
HDU1 - SCALE = 1.02 / Image scale (arcsec / pixel)
HDU1 - PIXSCALE= 1.02 / Image scale (arcsec / pixel)
HDU1 - GAIN = 139 / Camera gain
HDU1 - EGAIN = 4.96000003814697 / Electrons Per ADU
HDU1 - OFFSET = 20 / Camera offset
HDU1 - END

Check below screenshots, I just set a different Bayer pattern and reloaded the image in the image viewer:

RGGB:

GBRG:

BGGR:

GRBG:

When compared to this image from Diego Colonnello, it clearly seems that GBRG is the correct pattern for this image:

But when we check the other frame

M 20 Trifid Nebula_180sec_Bin 1x1_Gain 139_ASI Camera (1)_24C_0011.fit

Fits header:

FITS HDUs: 1
HDU1 - SIMPLE = T / file does conform to FITS standard
HDU1 - BITPIX = 16 / number of bits per data pixel
HDU1 - NAXIS = 2 / number of data axes
HDU1 - NAXIS1 = 4656 / length of data axis 1
HDU1 - NAXIS2 = 3520 / length of data axis 2
HDU1 - BZERO = 32768 / offset and data range to that of unsigned short
HDU1 - BSCALE = 1 / default scaling factor
HDU1 - CRPIX1 = 2328 / reference spectrum pixel coordinate for axis 1
HDU1 - CRPIX2 = 1760 / reference spectrum pixel coordinate for axis 2
HDU1 - CTYPE1 = 'RA---TAN' / standard system and projection
HDU1 - CTYPE2 = 'DEC--TAN' / standard system and projection
HDU1 - OBJECT = 'M 20 Trifid Nebula' / Object name
HDU1 - DATE-LOC= '2018-07-01T03:05:56' / Local observation date
HDU1 - DATE-OBS= '2018-07-01T07:05:56' / UTC observation date
HDU1 - IMAGETYP= 'LIGHT ' / Type of frame
HDU1 - CREATOR = 'Sequence Generator Pro v2.6.0.25' / Capture software
HDU1 - PROFILE = 'ZWO ASI1600' / SGPro profile name
HDU1 - INSTRUME= 'ASI Camera (1)' / Instrument name
HDU1 - OBSERVER= 'Thom Peters' / Observer name
HDU1 - SITENAME= 'Vicksburg, MI' / Observatory name
HDU1 - SITEELEV= 265 / Elevation of the imaging site in meters
HDU1 - SITELAT = '42d8m10.000s N' / Latitude of the imaging site in degrees
HDU1 - SITELONG= '85d33m8.000s W' / Longitude of the imaging site in degrees
HDU1 - EXPOSURE= 180 / Exposure time in seconds
HDU1 - CCD-TEMP= 24.2 / Camera cooler temperature
HDU1 - XBINNING= 1 / Camera X Bin
HDU1 - CCDXBIN = 1 / Camera X Bin
HDU1 - YBINNING= 1 / Camera Y Bin
HDU1 - CCDYBIN = 1 / Camera Y Bin
HDU1 - XPIXSZ = 3.8 / Pixel Width in microns (with binning)
HDU1 - YPIXSZ = 3.8 / Pixel Height in microns (with binning)
HDU1 - ANGLE = 0 / Image angle
HDU1 - SCALE = 0 / Image scale (arcsec / pixel)
HDU1 - PIXSCALE= 0 / Image scale (arcsec / pixel)
HDU1 - GAIN = 139 / Camera gain
HDU1 - EGAIN = 1.0011096841452 / Electrons Per ADU
HDU1 - END

the GRBG pattern is needed.

RGGB:

GBRG:

BGGR:

GRBG:

So this is rather odd to say the least. Since I assume that it's shot with the same camera, the explanation must be found in the capture software SGP Pro. Apparently, GRBG needs to be the correct pattern since I can read that on several sources on the internet if I google.

GBRG then can only be correct if the capture software did a flip of the captured data in the y-axis when storing the data.

Somehow, SGP Pro must provide doing this in the metadata, but I can't find it. I do see that different SGP versions were used:

M 20 Trifid Nebula_180sec_Bin 1x1_Gain 139_ASI Camera (1)_24C_0011.fit was shot with

HDU1 - CREATOR = 'Sequence Generator Pro v2.6.0.25' / Capture software

and

M 20 Trifed Nebula_120sec_gain_NA_offset_NA_Deg NA__frame13.fit

HDU1 - CREATOR = 'Sequence Generator Pro v3.0.2.91' / Capture software

By looking at the other metadata tags, clearly different settings were used in SGP per session.

What I would advise in this particalur case is:

• keep the data separate per session.  Don't use the multi-session mode.
• set the correct CFA pattern for the session and calibrate the data, save the calibrated data with the option, align channels. The saved frames are then already debayered properly.
• After having done this per session, you should have all frames calibrated and propely debayered.
• Load the calibrated, debayered frames as lights and process as usual.

That should do it 😉

What happened: since the different sessions needed a different CFA pattern, whichever pattern you chose, part of the frames were debayered with a wrong pattern which actually have opposing colors in Red and Blue, which also explains that the end results became quite colorless/green. The different sessions more or less neutralized the Red and Blue color of the other session... but green was maintained.

I hope this explains the issue. It's very odd and SGP Pro or some setting in SGP Pro is clearly to blame here if all data was shot with exactly the same camera but different settings in SGP, or different SGP version.

Mabula

Thanks!!!

Indeed there was an update to SPG, and I did not have the ASCOM version of the ZWO ASI1600 camera loaded for the first session.

What I think I'm going to do is delete all this data and reshoot with the new version of SPG and the ASCOM driver for the ASI1600 camera loaded. And I'll use the GRBG CFA selection for debayer.

I did shoot the M 13 Cluster with the new version of SPG, and the ASCOM driver for the camera loaded.  This is the result:

@thompeters,

Glad we got to the bottom of this 😉 I can really understand the confusion from mixing the data from both sessions which need a different CFA pattern.

Nice M13 !

Mabula