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Weird Rainbow-Colored Circles around DSO

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#1 Schleppafahrer

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Posted 06 February 2018 - 04:57 PM

Hey guys I just got my first tracked image of M42, it looked really good until I moved it into Photoshop and started processing it. There's a few weird Rainbow-colored Circles around it and I can't get rid of them. It kinda ruins the whole picture and I'm clueless as to how to deal with this. Has anyone experienced this before and might know a solution?

 

Kind regards

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#2 theastroimager

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Posted 06 February 2018 - 05:34 PM

Did you flat field this image?

 

Thanks,

 

John



#3 theastroimager

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Posted 06 February 2018 - 05:44 PM

Looking at it a little more, notice that the *circles* are not around the target, but are close to the center of the image, which makes me think that all you need to do to eliminate them is to flat field the image.

 

I would think that if you take an image with no DSO in it, you'll see the same result. 

 

Can you comment on the camera/telescope and exposure time? It would be helpful.

 

Thanks,

 

John



#4 Schleppafahrer

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Posted 06 February 2018 - 06:15 PM

By flat field do you mean flat frames? I just took a bunch of them and it's processing I hope that is what was missing. But yeah I believe what you see is right, the circles start from the center.

 

The picture is a Stack of ~ 30*60 second exposures taken with a Nikon D3300+Sigma 100-300 F4 lens.



#5 Schleppafahrer

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Posted 06 February 2018 - 06:31 PM

Well, I just took the stacked image with Flat frames into Photoshop and it's the same all over again. If you meant those by flat fielding then it didn't work. If you didn't, then please enlighten me. I'm kind of new to astrophotography



#6 SDTopensied

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Posted 11 February 2018 - 10:51 PM

Can you post one of your flat frames?

 

-Steve



#7 dayglow

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Posted 12 February 2018 - 11:35 AM

At what ISO setting are these images taken ?

Same question for flats.



#8 Schleppafahrer

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Posted 12 February 2018 - 09:05 PM

The shots were taken at ISO 800, I retook my flats and it worked out better, still very bad vignetting tho. (I attached a jpg screenshot of the flat frame I hope that's enough)

 

I have a similar issue with another shot taken recently, I again used flats for calibration, yet the picture shows severe vignetting and I'm not really sure how to deal with it. Any ideas/suggestions would be highly appreciated.

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#9 Dangitler

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Posted 12 February 2018 - 11:04 PM

I looks like dew to me.

#10 georgian82

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Posted 13 February 2018 - 12:18 AM

It might just be that you have to stop the lens down to f/5.6 and see if that fixes the issue.

Lenses are notorious for having uneven illuminated areas and stopping down sometimes helps.

#11 sharkmelley

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Posted 13 February 2018 - 01:24 AM

Where were your back-of-camera histogram levels for both your lights and your flats?   i.e. the peak of the histogram was how far in from the left hand side?

 

Many commercial cameras introduce changes of hue in the shadow areas so it's important to raise your data out of the shadows to prevent this happening.

 

Mark



#12 Schleppafahrer

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Posted 13 February 2018 - 07:11 AM

I looks like dew to me.

My lens didn't have any moisture on it so I doubt it is.

 

It might just be that you have to stop the lens down to f/5.6 and see if that fixes the issue.

Lenses are notorious for having uneven illuminated areas and stopping down sometimes helps.

Yeah I guess I'm going to have to do that. Even though I specifically bought an F4 Lens to soak up more light.

 

 

Where were your back-of-camera histogram levels for both your lights and your flats?   i.e. the peak of the histogram was how far in from the left hand side?

 

Many commercial cameras introduce changes of hue in the shadow areas so it's important to raise your data out of the shadows to prevent this happening.

 

Mark

The histogram of my flats is pretty much in the middle. As for the lights its spread out quite a bit but still centered.



#13 Schleppafahrer

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Posted 13 February 2018 - 08:54 AM

If anyone wants to have a go on my stacked tif, please feel free to do so. 

 

https://drive.google...ZC3qzrtzra0qDUN



#14 georgian82

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Posted 14 February 2018 - 12:24 AM

I understand your frustration and hesitation of stopping it down beyond f/4 which is the reason why you bought it in the first place. 

 

My guess the problem is that you are using a zoom lens and not a prime lens. I use a Nikkor 180mm ED f/2.8 lens and I get similar patters at f/2.8 but completely go away at f/4...but again, it is a prime lens. I assume that a zoom lens would make the issue more noticeable but I am not a lens expert so I cannot say for sure.



#15 Traveler

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Posted 14 February 2018 - 01:18 AM

I see these kind of artifacts quite often here on CN's DSLR dep, also with primes lenses by the way. In fact i have seen these things in my pictures (Nikon D5500 & Samyang 135 F2.0) as well.

Here i provide a recent CN thread about a Samyang 135mm F2.0 wich resulted in donut shapes in astropictures: link 
[ title: Samyang 135mm First Light with Nikon D5300 ]

 

The solution in that thread and with that optical system (Nikon D5300 & Samyang 135 F2): higher ISO, 800 in stead of 200....

But you, Schleppafahrer, are using ISO 800 already....

 

So the questions stays:

 

  1. -  what causes these artifacts,
  2. - is it something with Nikon DSLR's and fast lenses
  3. - what solutions are there to fix these Undesirable phenomena?


#16 georgian82

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Posted 14 February 2018 - 01:41 AM

 

I see these kind of artifacts quite often here on CN's DSLR dep, also with primes lenses by the way. In fact i have seen these things in my pictures (Nikon D5500 & Samyang 135 F2.0) as well.

Here i provide a recent CN thread about a Samyang 135mm F2.0 wich resulted in donut shapes in astropictures: link 
[ title: Samyang 135mm First Light with Nikon D5300 ]

 

The solution in that thread and with that optical system (Nikon D5300 & Samyang 135 F2): higher ISO, 800 in stead of 200....

But you, Schleppafahrer, are using ISO 800 already....

 

So the questions stays:

 

  1. -  what causes these artifacts,
  2. - is it something with Nikon DSLR's and fast lenses
  3. - what solutions are there to fix these Undesirable phenomena?

 

Did you ever experiment using that lens at f/2.8 or f/3.2? I bet you wouldn’t get those artifacts. 



#17 Traveler

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Posted 14 February 2018 - 02:19 AM

But what, georgian, cause these artifacts?



#18 georgian82

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Posted 14 February 2018 - 09:53 AM

But what, georgian, cause these artifacts?

I honestly don’t know. Again, I am not a lens expert or pretend to be one. But this is based on my personal experience with imaging with either zoom lenses and fast prime lenses. The issue does disappear if you stop the lens down enough. I saw thus same issue with my Nikon 180mm ed f/2.8 if shooting at f/2.8 and with my Sigma art 60mm f/2.8 if shooting at f/2.8. In both cases the issue disappears at f/4.

 

My best guess us that there is uneven illumination on the surfaces of each lens element (maybe not aligned properly?) You can kind of see that on the original post from the OP where there are a few rings around the target...seems to me that each one of those rings belongs to a lens element within the imaging train. But again, why this happens with zoom lenses or fast prime lenses is beyond my knowledge.


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#19 Schleppafahrer

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Posted 14 February 2018 - 10:19 AM

So I finally figured out what caused the issue. The main problem was the heavy light pollution from which I was taking my pictures. It enhanced the vignetting effect by alot and made it almost irreversible even with flats. By traveling ~10km out of the city centre I managed to get WAY better results, still showing some vignetting tho. However, after using a new method I found online (Roger Clark's method of processing) I managed to almost entirely remove the remaining artifacts, donut shapes etc. Funny part: I didn't use any flats, darks or bias frames at all. All I did was applying the lens profile correction and adjusting the white balance in Lightroom, convert the DNG files into TIFF and then stack them in DSS. If anyone is having similar issues, try that method. It works wonders!

 

Thanks to everyone for helping me tho, it's much appreciated.

 

Clear skies!

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#20 georgian82

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Posted 14 February 2018 - 01:10 PM

So I finally figured out what caused the issue. The main problem was the heavy light pollution from which I was taking my pictures. It enhanced the vignetting effect by alot and made it almost irreversible even with flats. By traveling ~10km out of the city centre I managed to get WAY better results, still showing some vignetting tho. However, after using a new method I found online (Roger Clark's method of processing) I managed to almost entirely remove the remaining artifacts, donut shapes etc. Funny part: I didn't use any flats, darks or bias frames at all. All I did was applying the lens profile correction and adjusting the white balance in Lightroom, convert the DNG files into TIFF and then stack them in DSS. If anyone is having similar issues, try that method. It works wonders!

 

Thanks to everyone for helping me tho, it's much appreciated.

 

Clear skies!

That's great! I am glad you found a solution!

 

Have you stretched the image to see if those artifacts are still there? Just a way to double check that the method you used to fix the issue really works, that way you know you can keep using it in the future.

 

Cheers,



#21 sharkmelley

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Posted 14 February 2018 - 02:07 PM

So I finally figured out what caused the issue. The main problem was the heavy light pollution from which I was taking my pictures. It enhanced the vignetting effect by alot and made it almost irreversible even with flats. By traveling ~10km out of the city centre I managed to get WAY better results, still showing some vignetting tho. However, after using a new method I found online (Roger Clark's method of processing) I managed to almost entirely remove the remaining artifacts, donut shapes etc. Funny part: I didn't use any flats, darks or bias frames at all. All I did was applying the lens profile correction and adjusting the white balance in Lightroom, convert the DNG files into TIFF and then stack them in DSS. If anyone is having similar issues, try that method. It works wonders!

 

 

Funnily enough I'm currently performing an extensive review of Roger Clark's controversial method.  Its strength is that you only need the lens profile and no flats, darks or bias.  Lack of lens profile is also its weakness - if you're using a telescope with no profile.

 

More importantly though, the ACR raw converter uses a variable gamma response curve which leads to colour saturation in the faint data and any light pollution subtraction is performed in this non-linear space, which generally leads to a bluing of the scene.  I can immediately see these effects in your final image - compare your second result with your first result which looks more or less correct (apart from the coloured rings of course).  Also, take a look at examples of Roger's work - they invariably suffer from crazy oversaturation.

 

I'll be writing all this up in the near future with examples that demonstrate what's happening and I'll post a link here on Cloudy Nights.

 

Mark


Edited by sharkmelley, 14 February 2018 - 02:58 PM.


#22 Schleppafahrer

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Posted 14 February 2018 - 11:00 PM

 

So I finally figured out what caused the issue. The main problem was the heavy light pollution from which I was taking my pictures. It enhanced the vignetting effect by alot and made it almost irreversible even with flats. By traveling ~10km out of the city centre I managed to get WAY better results, still showing some vignetting tho. However, after using a new method I found online (Roger Clark's method of processing) I managed to almost entirely remove the remaining artifacts, donut shapes etc. Funny part: I didn't use any flats, darks or bias frames at all. All I did was applying the lens profile correction and adjusting the white balance in Lightroom, convert the DNG files into TIFF and then stack them in DSS. If anyone is having similar issues, try that method. It works wonders!

 

 

Funnily enough I'm currently performing an extensive review of Roger Clark's controversial method.  Its strength is that you only need the lens profile and no flats, darks or bias.  Lack of lens profile is also its weakness - if you're using a telescope with no profile.

 

More importantly though, the ACR raw converter uses a variable gamma response curve which leads to colour saturation in the faint data and any light pollution subtraction is performed in this non-linear space, which generally leads to a bluing of the scene.  I can immediately see these effects in your final image - compare your second result with your first result which looks more or less correct (apart from the coloured rings of course).  Also, take a look at examples of Roger's work - they invariably suffer from crazy oversaturation.

 

I'll be writing all this up in the near future with examples that demonstrate what's happening and I'll post a link here on Cloudy Nights.

 

Mark

 

I've actually read quite a bit of your and Rogers (and Jon Ristas) debate, though I have to admit I only understand half of it. I'm a novice in astrophotography and am only trying to acquire new ways of enhancing my images. However I can see your point as to the outcome when using his methods. That being said I'm looking forward to your post!

 

Btw here's my final version, quite pleased with it!

 

Julian

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#23 jrsm

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Posted 16 February 2018 - 01:46 AM

Funnily enough I'm currently performing an extensive review of Roger Clark's controversial method.  Its strength is that you only need the lens profile and no flats, darks or bias.  Lack of lens profile is also its weakness - if you're using a telescope with no profile.

 

 

More importantly though, the ACR raw converter uses a variable gamma response curve which leads to colour saturation in the faint data and any light pollution subtraction is performed in this non-linear space, which generally leads to a bluing of the scene.  I can immediately see these effects in your final image - compare your second result with your first result which looks more or less correct (apart from the coloured rings of course).  Also, take a look at examples of Roger's work - they invariably suffer from crazy oversaturation.

 

I'll be writing all this up in the near future with examples that demonstrate what's happening and I'll post a link here on Cloudy Nights.

 

Mark

 

I have been following this discussion here and on  dpreview, with respect to colour rendition. On What are you basing your colour rendition?  Monitor or absolute colour values?   If you are trying to render colour from a 16  (48 bit rgb)  bit image in a 10 bit  ( 30 bit rgb) monitor, something is going to give.  I think the best discussions on colour rendition that I have seen are from Andrew Rodney. aka digitaldog.net. or Luminous Landscape.  I still haven't seen anything about monitor profiles or calibrated system.  So I am not sure what you are basing your colour rendition on.  

 




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