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Messed up M31....Help

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#1 DuPont

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Posted 25 September 2020 - 08:59 AM

Hi all, I've been imaging M31 lately & this example was shot two days ago. It consists of 44 subs at 240 seconds, 30 dark's, 30 flats & 50 bias frames for a total of 2:55 minutes integration time. Stacked in DSS & processed in StarTools with noise reduction.

EQ6-R mount, WO ZS103 scope with Flat./reducer on a Nikon D5600 unmodded.

This is really messed up & maybe some thoughts on whats happening here. As you can see there's really bad reddish banding along the bottom & upper right corner. My theory is #1: The seeing conditions were average but looking at a satellite smoke map there was smoke over my imaging site. #2: Forgot to turn on the dew heaters until I was about 2 hours into my session & it was a dewy evening. #3 Bad calibration frames?

Also, I imaged NGC7000 about 2 weeks prior & processed in the same manner with no problems.

This is not my best processing attempt as I want to emphasize the banding.

Any thoughts???

Attached Thumbnails

  • CN Test.jpg.jpg


#2 Gipht

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Posted 25 September 2020 - 09:18 AM

Trying a stack without any calibration files might be worth your time.  If the problem disappears, then you can do some detective work.  You would probably only have to stack 10 frames to see if calibrations are the problem.

 

This also be  to a bad file in the stack or calibrations.


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#3 DuPont

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Posted 25 September 2020 - 09:58 AM

Trying a stack without any calibration files might be worth your time.  If the problem disappears, then you can do some detective work.  You would probably only have to stack 10 frames to see if calibrations are the problem.

 

This also be  to a bad file in the stack or calibrations.

Thanks for the input & here is the same image which is a DSS stack of 10 with no calibration frames. It very well could be bad cal. frames but I won't know for sure until the next time out.

I also selected the 10 frames with the best score in DSS.
 

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  • CN Test #2.jpg.jpg


#4 limeyx

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Posted 25 September 2020 - 02:19 PM

What ISO ? The pattern of noise running across the bottom looks like the same pattern as my bias frames I took at 1600 but a little less severe

At 200ISO the bias is almost non-existent but I would imagine something like 800 would also have a similar pattern

 

I also see the tale-tell "circle" pattern in your first image (I have similar issues) -- I think this is supposed to be calibrated out with flats so I would suggest looking at your bias and flat frames for sure

 

Also the colors look off but maybe that's just the processing ?



#5 DuPont

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Posted 25 September 2020 - 05:09 PM

Subs were shoot at ISO200 & with an exposure time of 240 seconds. The histogram was between 1/4 & 1/3 from the left.

I've also seen the circle pattern in other images but not as much in this. I can't explain that ether.

Yes, the colors are off due to crummy processing but that I can correct.


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#6 Noobulosity

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Posted 26 September 2020 - 01:26 AM

Do you have any bad light frames?  Maybe a car drove by, shining lights into your scope?  Those gradients seem weird, and they aren't consistent in your two stacks.  It seems odd that it would change when you stack different sets of exposures, so I would start sifting through the lights to see if something's off about one or more of them.



#7 DuPont

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Posted 06 October 2020 - 08:54 AM

So here is my latest attempt at M31. Getting better but still need a lot more integration time.

Whats changed? #1 I ditched the LP filter. #2 I had a night without smoke in the atmosphere. #3 I moved from my driveway to the back lawn where there's less light pollution from street lights. #4 I found the main scope glass was in need of cleaning....lesson learned.

116 x 60 sec. & 30 x 90 sec. lights = 2.65 hours. 30 dark's, 30 flats, 50 bias frames.

Dithered & DSS stacking with 2x drizzle.

Processed in Star Tools.

Still not happy with the color processing but I'm thinking I need at least another 5 hours under the stars.

Imaging with my WO ZS103 & WO flat/reducer at FL of 569mm.

Attached Thumbnails

  • M31 10-6-2020.jpg.jpg

Edited by DuPont, 06 October 2020 - 08:57 AM.


#8 F.Meiresonne

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Posted 06 October 2020 - 09:25 AM

Don't think you need more integration time. Just needs a slight diminishing of the yellow center, otherwise a great image..imo




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