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Can Someone Diagnose these Veil Nebula Miss-fires?

CMOS EAA dso equipment reflector
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#26 GoFish

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Posted 23 September 2019 - 10:33 PM

Thanks Rick. I’ll check it out. 

Vignetting hasn’t been an issue until I started viewing nebulas. 

G. 

The stretching needed to bring out nebula details also reveals vignetting.  Just the cost of doing business. 

 

Without flats, it was terrible with my HyperStar 8. But once you learn to love taking flats, vignetting is not really an issue. 



#27 Rickster

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Posted 24 September 2019 - 10:08 AM

This post is for users of Astrotoaster.  It describes a feature that is available in Astrotoaster and not SharpCap.

 

Astrotoaster has a "LensGrad" slider that lets you dial in varying degrees of radial correction (both positive and negative).  It also allows use of flats if you prefer.  Not only can the LensGrad tool be used to compensate for vignetting (with or without flats), it can also be used to either bring out or suppress the center of the image.  This is handy when you want to accentuate (or attenuate) a galaxy or nebula core.  For example, M31 and M42 have bright cores that will saturate (blow out) if the gain is increased enough to see details in the outer parts of the field.  The LensGrad tool lets you dial down the center.  Conversely, some galaxies have dimmer cores.  These can be made to pop if the center of the image is accentuated.  Again, this tool is available with or without flats.



#28 Astrojedi

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Posted 24 September 2019 - 01:18 PM

1. You need to use a light pollution or nebula filter.

2. Need to crop your capture to eliminate the area with vignetting - Makes stretching very difficult. Flats will not fix this much vignetting.

3. If possible use a shorter focal length scope e.g. refractor for large objects.

 

 

Here is a single 300s unprocessed and uncalibrated frame using ASIAIR, ASI183MC, Optolong CLS CCD filter, and AT60ED+Flattener. This was taken from my red/white LP zone backyard with average transparency (I get a lot of moisture from the ocean)

 

 

post-243927-0-56555200-1562006959.jpg

 

 


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#29 GaryShaw

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Posted 24 September 2019 - 01:27 PM

AJ

I assume that the 'cropping' retains the subject area that is within the round vignette area....so, I crop the circular area so you don't notice the darker surrounding area, then adjust that? I'm hoping the filter will eliminate most of the vignette. I exaggerated the vignette here to make the issue clear.

thank you for your input.

Gary




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