Background artifact issue: Page 2

Background artifact issue

jmtanous

Hi,

Since the calibration images don't fully match the properties of the light frames there is no way to correct this issue. There might be some workarounds in postprocessing where you can 'hide' the background residual artifacts but in doing so it is inevitable to remove weak real signals. For instance, I don't use noise reduction at all in my workflow to prevent damage to the week fine details of my images.

Would it be possible to trade in this camara and get another model? For instance, I am interested in the ASI071pro, are you willing to take my ASI294 and replace it with an ASI071pro? I am willing to pay shipping and price difference.

Regards,

Jose

Support@ZWO

Please send us a email to support(at)zwoptical.com

mvas

What was the FINAL SOLUTION to this problem?

Sam@ZWO

ASI294 is a very good camera but we cannot control the sensor's behavior

it's very easy to remove these faint artifacts in post-processing

wargrafix

Wasn't this issue related to the tec cooler?

Support@ZWO

wargrafix wrote:
Wasn't this issue related to the tec cooler?

Not the cooler.

wargrafix

Sean.Wang wrote:
wargrafix wrote:Wasn't this issue related to the tec cooler?

Not the cooler.

Then what?

bulrichl

Sean.Wang wrote:
wargrafix wrote:Wasn't this issue related to the tec cooler?

Not the cooler.

In this thread, users of the ASI294MC Pro and several people that are interested in purchasing this camera have put their questions about the cause of this artifact. Unfortunately these questions have not been responded in an adequate manner.

You told us what is NOT the cause of the artifact (the tec cooler) - so, please answer our question: what is it then?

Bernd

Sam@ZWO

unlike CCD, CMOS is not a pure sensor IC

it builds in a lot of circuit like power, PLL, AD etc.

all these circuits affect the final output of one image

if there is such noise of the camera, it comes from the sensor

we can do nothing

so don't use the CMOS camera beyond its limit

294 is a very good sensor for astrophotography

but if you need to stretch the background heavily and no noise find

CCD is a better choice for such purpose

wargrafix

So, it's a case of overstretch vs length of exposure or total exposure time?

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.

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

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.

Support@ZWO

You are welcome!

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.

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.

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

Support@ZWO

Dunc wrote:

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.

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.

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?

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