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Pinwheel - Rings on stacked image

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#1 EC_EFC

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Posted 19 September 2020 - 04:49 AM

Hi all,

 

Processed a few images I took the other night of the pinwheel galaxy. The processed image is a crop and isn’t pretty, but I was just glad I was able to pull some data and see the galaxy.

The stacked image has some weird circles on it which I was hoping someone could help with.

 

Stacked image unprocessed - https://flic.kr/ps/3SpbhM

Really rough crop / processed in about 2 mins - https://ibb.co/gMn1mtT

 

Gear - EQ6 GT Mount
6” Newtonian - TS Optics - Photon
F4 coma corrector
6D

 

8x 30 second exposures at 1250 iso

1x 38 second at 1250
5x 1 minute at 800
1x 40 at 800

 

No calibration. (I know I should, but it was second night with the setup and didn’t expect to have got anything usable)

 

Are the circles on it Newtonian rings?

What caused it, the scope/camera sensor/coma corrector or is it due to the different exposures being stacked?

Thanks

 


Hi all,

 

Processed a few images I took the other night of the pinwheel galaxy. The processed image is a crop and isn’t pretty, but I was just glad I was able to pull some data and see the galaxy.

The stacked image has some weird circles on it which I was hoping someone could help with.

 

Stacked image - https://flic.kr/ps/3SpbhM

 

Gear - EQ6 GT Mount
6” Newtonian - TS Optics - Photon
F4 coma corrector
6D

 

8x 30 second exposures at 1250 iso
1x 38 second at 1250
5x 1 minute at 800
1x 40 at 800

 

No calibration. (I know I should, but it was second night with the setup and didn’t expect to have got anything usable)

 

Are the circles on it Newtonian rings?

What caused it, the scope/camera sensor/coma corrector or is it due to the different exposures being stacked?

Thanks


Edited by EC_EFC, 19 September 2020 - 05:37 AM.

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#2 Tapio

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Posted 19 September 2020 - 05:26 AM

Can't see much on your example image.
But my educated guess is dust motes if you didn't take flat frames.

#3 EC_EFC

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Posted 19 September 2020 - 05:55 AM

https://i.postimg.cc...0-F4-E9-EF6.jpg

 

you can see the circles on the outside in this version


Edited by EC_EFC, 19 September 2020 - 06:17 AM.


#4 copper280z

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Posted 19 September 2020 - 07:59 AM

That's from your lack of calibration, flats (and the rest) will fix it.


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#5 EC_EFC

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Posted 19 September 2020 - 12:05 PM

Thanks! I’ll be sure to try again and take some
Calibration frames.

#6 EC_EFC

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Posted 19 September 2020 - 12:05 PM

Thanks! I’ll be sure to try again and take some
Calibration frames.

#7 speedster

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Posted 19 September 2020 - 01:12 PM

I get those same rings sometimes.  I'm no expert and my data comes from Bortle 8 skies and I have to be pretty aggressive in processing.  Background gradient removal techniques in PS cause them for me when I'm too aggressive.  Carboni's tools can also cause them for me sometimes.  They can get much worse than what you are seeing in your image.  Instead of  large linear stretch, I do many small stretches to sneak up on the point when the rings appear.   Basically moving the left histogram slider half way to the hump and the middle slider half way to the hump.  This may take 5-8 iterations until it looks like I've done all I can without making the rings appear.  Sometimes resetting the black point helps.  I hope someone way smarter than me chimes in to tell us what processing step causes these artifacts.



#8 EC_EFC

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Posted 19 September 2020 - 03:05 PM

This was from a bortle 8 too, so that makes sense.

Thanks.


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