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Re: Background artifact issue

Posted: Fri Oct 12, 2018 6:08 am
by Support@ZWO
wargrafix wrote:So, it's a case of overstretch vs length of exposure or total exposure time?
length of exposure of single frame depand on the background level.

Re: Background artifact issue

Posted: Fri Oct 12, 2018 11:46 pm
by wargrafix
Sean.Wang wrote:
wargrafix wrote:So, it's a case of overstretch vs length of exposure or total exposure time?
length of exposure of single frame depand on the background level.

Please clarify. I normally shoot 8 second to 1 minute per exposure

Re: Background artifact issue

Posted: Mon Oct 15, 2018 1:43 pm
by Support@ZWO
wargrafix wrote:
Sean.Wang wrote:
wargrafix wrote:So, it's a case of overstretch vs length of exposure or total exposure time?
length of exposure of single frame depand on the background level.

Please clarify. I normally shoot 8 second to 1 minute per exposure
If the sky is very dark, try 3-5min to get better SNR.

Re: Background artifact issue

Posted: Wed Jan 23, 2019 3:17 am
by Support@ZWO
You are welcome!

Re: Background artifact issue

Posted: Sat Feb 16, 2019 10:34 am
by Dunc
Hi,

I have been following this thread and have the same issue with my ASI294MC Pro. Is there any progress? I have been experimenting with exposure length, cooling set point (did a test at zero degrees C last night, ambient 3C so no cooling stress), flats light source. I have been able to only get a couple of good images out of this camera and that was when I first got it at the end December 2017. I have kept drives updated. Is there a chance of downloading the driver from that date to try in case the newer drives have caused the problem?
I'm fed up and if I can't resolve this soon I will have to try and sell the camera.

Thanks

Duncan

Here's an example of what I am getting. This was taken at Astrofarm in central France with very dark skies.

Image

Re: Background artifact issue

Posted: Thu Feb 21, 2019 3:01 am
by Support@ZWO
Hi there
reduce the exposure time and 30c below the ambient is the best way we found right now.
Sorry to tell that we didn't find a better solution to calibrate the artifact.

Re: Background artifact issue

Posted: Fri Feb 22, 2019 10:51 am
by Dunc
Thanks for the reply. Could this problem be related to the IMX294-CJK sensors Quad Bayer Coding HDR function? How can I be sure that the CMOS chip was not activating this feature and was only doing the straight pixel binning? It could explain the colour blotches if HDR processing was being carried out.

Also I have been experimenting with dark frames. There seems to be a difference in the darks produced by the native driver (ASICAP and Sharpcap used) and the ASCOM driver (APT, N.I.N.A. used). See my post on my astronomy societies forum. This could explain why so many people including me have found it impossible to apply calibration frames to images. I am going to take some flat field images with ASICAP today and try calibrating some lights I took with ASICAP last night. I have stuck to 300s, gain 120, offset 28, cooling to 0C for consistency.

Thanks

Duncan

Re: Background artifact issue

Posted: Tue Feb 26, 2019 7:50 am
by Support@ZWO
Dunc wrote:
Fri Feb 22, 2019 10:51 am
Thanks for the reply. Could this problem be related to the IMX294-CJK sensors Quad Bayer Coding HDR function? How can I be sure that the CMOS chip was not activating this feature and was only doing the straight pixel binning? It could explain the colour blotches if HDR processing was being carried out.

Also I have been experimenting with dark frames. There seems to be a difference in the darks produced by the native driver (ASICAP and Sharpcap used) and the ASCOM driver (APT, N.I.N.A. used). See my post on my astronomy societies forum. This could explain why so many people including me have found it impossible to apply calibration frames to images. I am going to take some flat field images with ASICAP today and try calibrating some lights I took with ASICAP last night. I have stuck to 300s, gain 120, offset 28, cooling to 0C for consistency.

Thanks

Duncan
Yes, that would be helpful.

Re: Background artifact issue

Posted: Wed Mar 27, 2019 9:49 am
by Dunc
Hi Sean,

I have resolved the issue with the background artifacts. I used SharpCap Pro to do a Sensor Analysis and then used the Smart Histogram tool to suggest an exposure for my sky conditions which are Bortle 4, 21.45 so quite nice. The exposure recommended was 255s at gain 120 with an Offset of 4. The drivers default to 28 and 30 (ASCOM/direct) on my laptop when clean installed. With an offset of 4 I get lovely data.

This image was captured with N.I.N.A. 1.8 RC0006 and processed with DSS4 and StarTools - I am not the best at this but I am very happy with this result from 1h 30m of data. I processed with 10 Darks, 10 Flats and 10 Dark Flats at -15c. I did not use Bias frames because minimum duration Bias/Offset frames are not as with a CCD or older DSLR with this camera and don't work in the traditional calibration workflow as expected possibly due CMOS on board processing.

Image

Re: Background artifact issue

Posted: Mon Apr 01, 2019 12:17 pm
by khrrugh
The exposure recommended was 255s at gain 120 with an Offset of 4. The drivers default to 28 and 30 (ASCOM/direct) on my laptop when clean installed. With an offset of 4 I get lovely data.
Can anyone confirm Duncs settings? An offset of 4 sounds strange for me, but if it works for you, Dunc, maybe i should give it a try? Or are we loosing too much dynamic range with this setting?