Help with banding stacking issues

B

b36lbx

Member
Hi all,

I need some help to understand what is going wrong with my Ha stacking. This is the first time I use Bin2 on my 1600mm pro, never had any banding issues in the past . I've included snips of all master files - dark, flat_dark, flat and the stacked Ha image.
Filter is the new 3nm Antlia, exposure time was 300s for the Ha files (76 in total), OTA is a reduced Celestron Edge 8 with 1600mm pro Bin 2, Gain 0.
For stacking I've used the WBPP 2.0 script.

Many thanks
 

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  • Flat.JPG
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  • H.JPG
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  • flat_dark.JPG
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Looks like the MasterDark does not match the Ha subframes. The JPGs are not helpful, one would need the masters (dark, flat) and some light frames in order to assist.

Bernd
 
I subtracted the MasterDark from the first of your Ha subframes with PixelMath. The result is shown in the appended screen section (image with vertical banding, histogram, statistics):
- The histogramm shows that severe clipping occurred.
- The statistics show a count (%) value of 88.08 %, i.e. about 12 % of the pixels are clipped in the low range.
This is typical for either short exposure time or (in your case) for usage of narrow band filters.

In order to avoid clipping you will have to use an output pedestal in ImageCalibration. This is not possible with the current WBPP version 2.02, but output pedestal will be supported in WBPP v2.1. For the time being, you will have to perform image calibration with the ImageCalibration process. The output pedestal has to be set in the 'Output files' section, a value of 100 DN normally will suffice. In ImageIntegration, the option 'Subtract pedestals' has to be unchecked (this is the default).

Good luck with the manual image calibration!

Bernd
L_cal.JPG
 
bulrichl said:
I subtracted the MasterDark from the first of your Ha subframes with PixelMath. The result is shown in the appended screen section (image with vertical banding, histogram, statistics):
- The histogramm shows that severe clipping occurred.
- The statistics show a count (%) value of 88.08 %, i.e. about 12 % of the pixels are clipped in the low range.
This is typical for either short exposure time or (in your case) for usage of narrow band filters.

In order to avoid clipping you will have to use an output pedestal in ImageCalibration. This is not possible with the current WBPP version 2.02, but output pedestal will be supported in WBPP v2.1. For the time being, you will have to perform image calibration with the ImageCalibration process. The output pedestal has to be set in the 'Output files' section, a value of 100 DN normally will suffice. In ImageIntegration, the option 'Subtract pedestals' has to be unchecked (this is the default).

Good luck with the manual image calibration!

Bernd
Click to expand...
Hey Bernd - thanks for the advice, I have tried to restack as per your instructions, unfortunately the result is not much better.
I've attached it here for reference: https://drive.google.com/drive/folders/1bW4aWqRqwqboQKtj7TvS0oa37PNPlh6G?usp=sharing
 
I am surprised. Then your dark frames are not consistent with the light frames for whatever reason.

For lack of dark frames I cannot compare the FITS headers. Could you please upload a few dark frames (that were used to generate the MD) additionally?

Bernd
 
I don't see any differences in binning, gain, offset, exposure time and temperature between your light and dark frames. I integrated the dark frames and obtained the same MasterDark as you. This MD does not correct "amplifier glow" completely nor does it remove the vertical banding competely. So I can fully confirm your findings.

Did you use dark frame optimization in the ImageCalibration process? If the answer is no, I can imagine only one reason for the issue: gain 0.

Did you use gain 0 before?
Did you use gain 0 in combination with a narrow band filter before?
Did you use gain 0 in combination with a narrow band filter and 2x2 binning before?

Jon Rista (who is an expert with this camera) does not recommend to use gain 0 with the ASI1600MM, especially not in combination with narrowband filters. He uses gain 200 or gain 139 for narrowband and gain 76 for broadband. An interesting discussion is e.g. https://www.cloudynights.com/topic/...e-zone-narrowband-imaging-with-asi1600mm-pro/ . Jon's reasoning is summarized nicely in post #11, but the whole thread is worth reading.

Finally I found a thread which exactly describes your issue. Have a guess - correct, ASI1600MM at gain 0:
https://www.cloudynights.com/topic/653669-asi1600mm-pro-vertical-lines/ . Please absolutely read both of these threads!

In my view you have to stop using gain 0 with this camera, especially in combination with narrowband filters.

Bernd
 
bulrichl said:
I don't see any differences in binning, gain, offset, exposure time and temperature between your light and dark frames. I integrated the dark frames and obtained the same MasterDark as you. This MD does not correct "amplifier glow" completely nor does it remove the vertical banding competely. So I can fully confirm your findings.

Did you use dark frame optimization in the ImageCalibration process? If the answer is no, I can imagine only one reason for the issue: gain 0.

Did you use gain 0 before?
Did you use gain 0 in combination with a narrow band filter before?
Did you use gain 0 in combination with a narrow band filter and 2x2 binning before?

Jon Rista (who is an expert with this camera) does not recommend to use gain 0 with the ASI1600MM, especially not in combination with narrowband filters. He uses gain 200 or gain 139 for narrowband and gain 76 for broadband. An interesting discussion is e.g. https://www.cloudynights.com/topic/...e-zone-narrowband-imaging-with-asi1600mm-pro/ . Jon's reasoning is summarized nicely in post #11, but the whole thread is worth reading.

Finally I found a thread which exactly describes your issue. Have a guess - correct, ASI1600MM at gain 0:
https://www.cloudynights.com/topic/653669-asi1600mm-pro-vertical-lines/ . Please absolutely read both of these threads!

In my view you have to stop using gain 0 with this camera, especially in combination with narrowband filters.

Bernd
Click to expand...
Bernd, many thanks for spending all of this time trying to get to the bottom of my stacking issue.
I can safely answer 'No' to all of your questions and unfortunately everything you just mentioned is a confirmation of my fears in regards to Gain 0 on the 1600mm pro. I just wish I would've done some research before investing over 20h into a project while trying something completely new as all other filter masters have some degree of artefacts.
 
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