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Noise in pictures from ASI2600MC

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#1 taipan

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Posted 16 October 2021 - 03:08 AM

Yesterday i tried my new camera. After stacking about 20 300s subs with 20 darks and 20 flats in DSS the stacked picture still is very grainy… The same amount of pictures from my old ASI294MC was much less grainy.

Used my ASIAIR and gain 100.

Andy ideas  if something colud be wrong? Is  there a way to check if the camera is working with 16bit or if the HCG is realy  turning on.



#2 Poochpa

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Posted 16 October 2021 - 10:02 AM

Did you use dithering? If not, dithering will greatly help.  If you dithered, how often? Every frame, every other frame, every x frame? With just 20 lights, I would dither at least every other frame. Also, you didn't mention whether you cooled the camera. I cool mine to -5 or -10c, depending on ambient temps.

Mike



#3 RazvanUnderStars

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Posted 16 October 2021 - 04:53 PM

'A picture is worth a thousand words'- post one so we can see what kind of noise you got. Besides what Mike asked already,it matters what object you shot, what light pollution you had and, possibly, what processing workflow you used.


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#4 TelescopeGreg

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Posted 16 October 2021 - 05:40 PM

What scope (focal ratio), and did you use the cooler?  Offset setting?  What were you aimed at?

 

I did 20 x 300s, gain 100, offset 50, temp -5C last night, and it came out very nice.  5" f/7 scope.  There was some noise, but I was imaging a rather dim nebula at the time, and it processed out pretty well.  The only thing I have to compare it with was my old DSLR, and the 2600 is much better than it.



#5 PatrickVt

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Posted 16 October 2021 - 06:51 PM

I agree with all the above.  We need to know all the specifics...  telescope model as well as all the camera settings.  A sample image with an explanation of the processing involved would help significantly as well.   I have found that many people think they can just use the same settings that they used with a different/previous camera and expect that those settings are the ideal settings for the new camera.  It doesn't necessarily work that way.  Actually, it rarely works that way.  

 

Once all the specifics are stated, those with the same camera can provide advice based on their experience.  

 

Patrick



#6 taipan

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Posted 20 October 2021 - 11:59 AM

This is 30 subs of the Boubble nebula. Used dithering every 3 pics. Gain100, -10C

Flats and darks and Bias.

Had to lower the resolution by 70% to get the file under 500K but you can se that its grainy.

Only did autostretch and colourcalibration in PI

 

Attached Thumbnails

  • Bubblelag.jpg


#7 taipan

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Posted 20 October 2021 - 12:12 PM

This is the Wall taken with the same telescope. TS Photoline115 and my old ASI294MC 300s, Gain120,-10C

20subs stacked with darks and flats. Did the same autostretch in PI and colourcalibration as tha picture of the Boubble.

 

Attached Thumbnails

  • Walllag.jpg

Edited by taipan, 20 October 2021 - 12:13 PM.


#8 WadeH237

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Posted 20 October 2021 - 12:17 PM

Had to lower the resolution by 70% to get the file under 500K but you can se that its grainy.

It's really difficult to tell from a JPG, but that looks more like sharpening artifacts to me than noise in the background sky.  Can you tell us how your processed it?

 

I have an ASI2600MC Pro as well, and I think that it produces really nice data.  But I typically do much longer integrations.  There is less than 2 hours of data in this sample.



#9 taipan

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Posted 20 October 2021 - 12:28 PM

It's really difficult to tell from a JPG, but that looks more like sharpening artifacts to me than noise in the background sky.  Can you tell us how your processed it?

 

I have an ASI2600MC Pro as well, and I think that it produces really nice data.  But I typically do much longer integrations.  There is less than 2 hours of data in this sample.

30*300s=2,4hour. I kvow its not much but with the same amount with the 294 the noice is better..

No processing, just autostretch and color calibration. And converted to JPeg 500Kb to be able to post here



#10 WadeH237

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Posted 20 October 2021 - 01:39 PM

30*300s=2,4hour. I kvow its not much but with the same amount with the 294 the noice is better..

No processing, just autostretch and color calibration. And converted to JPeg 500Kb to be able to post here

Can you crop the image to an area with some nebula and some background sky, but be able to save it has high quality without being too large?  Even better, could you make the integrated FITS file available with no processing or stretching?

 

It's really not possible to diagnose what's going on with the small scale JPG artifacts.

 

Regarding the time, I misread and thought that you have 20x300 subs.  It's still not a lot of integration time.


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#11 Psychlist1972

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Posted 21 October 2021 - 01:58 AM

This is 30 subs of the Boubble nebula. Used dithering every 3 pics. Gain100, -10C

Flats and darks and Bias.

Had to lower the resolution by 70% to get the file under 500K but you can se that its grainy.

Only did autostretch and colourcalibration in PI

Did you inspect the subs to see if any are especially bad? I can clearly make out the edges of a rotated frame, rather than a gradient of many frames, but I suppose that depends on how your stacker works, but if it's actual image train rotation (like a loose adapter ring), that might explain some things. 

 

The 2600 is also a very sensitive camera and has smaller pixels and smaller well capacity than the 294. You may consider doing more subs at a lower exposure time to see if that works better for you.

 

Finally, the value of 100 for gain looks good on graphs, but isn't necessarily spot on. For example, on my 533mc pro, I use 103 to get a low noise photo.

 

Pete


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#12 Peteram

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Posted 21 October 2021 - 01:00 PM

Also it seems to me that the signal in the Bubble nebula is not quite as strong as in the wall. So maybe it was stretched a lot more. I find the signal in my 2600 to be very clean.




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