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Nebula Color Bleeding Into Dark Space

Astrophotography Beginner
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#1 Spangz

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Posted 17 September 2021 - 09:19 AM

Why am I getting color bleeding and diagonal banding into the dark parts of my imaging. Am I stretching the image to far, do i need more data. this effect is making it really hard to process and display the contrast between the nebula and dark space.

North American Nebula

-60 mins of lights

-60 mins darks

-Skywatcher 72ed

-70D Canon

-SkyGuider Pro

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  • backyard NAN-Recovered.jpg

Edited by Spangz, 17 September 2021 - 09:22 AM.


#2 sharkmelley

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Posted 17 September 2021 - 09:35 AM

The diagonal streaking is the so-called walking noise.  Your framing has drifted during the imaging session, so the hot and warm pixels have "drifted" across the stacked image.

 

It's cured using a combination of:

  • Dark calibration
  • Dithered acquisition
  • Outlier rejection during stacking

Mark


Edited by sharkmelley, 17 September 2021 - 09:41 AM.

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#3 jonnybravo0311

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Posted 17 September 2021 - 09:38 AM

Assuming that Canon is not astro-modified, the answer is because a whole lot of the light you're trying to capture is being blocked. There is a filter in front of your sensor that blocks the deep reds, to which the Hydrogen-alpha emission belongs.

 

It's not that the nebulosity is "bleeding" into the dark space. It is that your camera is blocking a lot of the emitted light, so you have to stretch it considerably just to see anything, which in turn is exposing the underlying noise.

 

The most obvious noise component is as Mark just wrote in his response: walking noise.

 

Solution for the signal: a whole lot more total integration time, or modification of the camera to remove that filter, or purchase of a dedicated astrophotography camera.

 

Solution for the walking noise: see Mark's response smile.gif


Edited by jonnybravo0311, 17 September 2021 - 09:40 AM.

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#4 imtl

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Posted 17 September 2021 - 09:48 AM

In the OP's specific case, dithering will yield an even worse result since the skyguider pro only tracks (therefore dither) in RA.



#5 bobzeq25

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Posted 17 September 2021 - 10:54 AM

As others have said, this is normal.  There's a _lot_ of faint nebulosity around the NA, the streaks are fixed pattern noise, removed by dithering.  Diithering in RA only can work (and may not), it depends on a number of factors.



#6 unimatrix0

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Posted 17 September 2021 - 11:26 AM

There seems to be a tracking issue , the stars look elongated on the same direction as the walking noise. 



#7 Spangz

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Posted 17 September 2021 - 12:18 PM

Thanks guys for all the answers quick question do I need to guide be able to Dither

#8 jonnybravo0311

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Posted 17 September 2021 - 01:18 PM

For your tracker? Yes. Unless you want to "manually" dither by randomly moving the mount in RA/Dec every so often :p. As others have stated, if you do introduce a guiding solution, because of the design of your tracker (only has a motor in RA), you can only dither in RA.


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