Banding issue: ASI 1600 Mono Cool, HDR

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Farzad_K
Posts: 16
Joined: Wed Nov 30, 2016 4:26 am

Banding issue: ASI 1600 Mono Cool, HDR

Post by Farzad_K » Sun Feb 10, 2019 11:56 pm

Hello.

I have been struggling with this issue I recently discovered as I transitioned from RGB into NB imaging. I use the standard HDR setting of ZWO which is associated with a zero gain and for high dynamic range. At 300 second I notice vertical bands in dark masters and also light masters and they don't get calibrated out with or without use of bias masters. I wonder if anyone else has experienced this and if it is a normal behavior.

I have attached a screenshot from the dark master, 300 seconds, -20 degrees, HDR

Thanks

Farzad
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2019-02-10_15-54-08.png

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chad
Posts: 527
Joined: Thu Feb 09, 2017 4:58 am

Re: Banding issue: ASI 1600 Mono Cool, HDR

Post by chad » Tue Feb 12, 2019 6:09 am

Hi Farzad,
Like I said in that post.
If it could be seen in your light field, please use dark field and flat fields to calibrate it. Beside, there is no need to use the bias fields to make the calibrate again.
We also asked the sensor manufacturers for further reasons, and they didn't have a firm response. The difference between the noise and normal is very small for them. So at the moment we're not sure what noise it is. I can only tell you that there is no need to use a bias field for calibration.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

Farzad_K
Posts: 16
Joined: Wed Nov 30, 2016 4:26 am

Re: Banding issue: ASI 1600 Mono Cool, HDR

Post by Farzad_K » Tue Feb 12, 2019 7:14 am

Chad,

This has nothing to do with biases. This is a master dark that is produced using the HDR setting. I am asking what is the reason for the vertical lines and if this is normal. The lights are the same way, they have vertical lines. These darks are not able to calibrate out the vertical lines from the lights. I have tried with and without biases and it makes no difference.

At the moment I am down to looking at the dark issue. Is this a normal result of the ZWO camera set to HDR?

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chad
Posts: 527
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Re: Banding issue: ASI 1600 Mono Cool, HDR

Post by chad » Wed Feb 13, 2019 2:14 am

Hi Farzad,
So now, you have 2 problems.
1st, What cause this vertical line. And is it normal?
2nd, You could not celibrate the light filed with dark field.
Am I right?
If I am right, for the reason, sorry, we do not know. We think this may be the inconsistency of the ADC inside the Sensor. But we don't have enough evidence. Sensor manufacturers have not told us much about this problem. And it is normal for our camera. According to my experience, all of the CMOS sensor have this kind of problem.
For the calibrate, I am not sure, I did not test it, just Tom said he did it success, I know this news 2 days ago. I will ask my colleague Sean to make a test. And I will send out an email to you and Sean. You can ask help from him.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

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Sam
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Re: Banding issue: ASI 1600 Mono Cool, HDR

Post by Sam » Wed Feb 13, 2019 8:28 am

the vertical line is normal just like master bias frame
you can calibrate like this if you don't want to take bias frame
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ZWO Founder
Location:lon=120.6 lat=31.3
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