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(@pswilson1)
Main Sequence Star Customer
Joined: 9 months ago
Posts: 29
November 26, 2020 19:36  
California raw stack

Does anyone have an opinion about where the vertical light bands on the left and right edges are coming from?  This required so much cropping that I wasn't able to get it all and keep the large nebula intact. This image was the result of 310, 60 second subs using a RASA 8 at F/2, an Optolong L-extreme filter, and a ASI533 OSC camera, unity gain.  Dithering at every 2nd frame, 10 pixels.  Flats, dark flats, and darks duly acquired and applied.  There was a meridian flip as well.

Happy for any criticism or suggestions which could enable me to get a better result next time.  Artifacts like this have been occurring repeatedly, and I don't know what is causing this problem.


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(@wvreeven)
Black Hole Admin
Joined: 2 years ago
Posts: 484
November 26, 2020 19:44  

@pswilson1

Hi Paul,

Those edges are caused by the fact that the subs do not exactly overlap because of dithering. You see the regions where there was less signal accumulated because less frames cover those areas. You can blend those edges better by enabling MBB in tab 6. The black edges will not disappear and the only way to get rid of them is to crop.

 

Wouter


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(@pswilson1)
Main Sequence Star Customer
Joined: 9 months ago
Posts: 29
November 26, 2020 20:38  

@wvreeven  Thanks.  But I DID enable MBB and I always do.  This remains a serious problem.  

I am between a rock and a hard place.  If I don't dither heavily, I get pattern noise.  

This post was modified 2 months ago by Paul Wilson

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(@wvreeven)
Black Hole Admin
Joined: 2 years ago
Posts: 484
November 26, 2020 20:50  

@pswilson1 What value did you set MBB to? The default 5%? If yes, try a higher value like 10 or even 15% and see if that helps.

Dithering really is useful, even if that means having to sacrifice some of the FOV. The California Nebula seems to be a pretty large object for your telescope and camera anyway and I understand that it is hard to crop that beautiful image!


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(@pswilson1)
Main Sequence Star Customer
Joined: 9 months ago
Posts: 29
November 26, 2020 22:19  

@wvreeven

Yes, default.  Thank you, I will definitely try setting this MBB value higher as this problem has recurred several times.


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(@mabula-admin)
Universe Admin
Joined: 4 years ago
Posts: 2508
November 27, 2020 15:15  

Dear Paul @pswilson1,

I see that the difference in Field of View for your light frames changes a bit. Now in combination with the strong signal of the nebulosity I would suggest you to try:

5) Normalize, use advanced normalization

I think that should fix it 😉

If not entirely okay yet, enable LNC first degree with a couple of iterations. That should really fix it in combination with MBB 10% roughly.

Please let us know if this helps 😉

Mabula


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(@pswilson1)
Main Sequence Star Customer
Joined: 9 months ago
Posts: 29
November 28, 2020 00:18  

@mabula-admin

corrected cal nebula

 Wow!  Those suggestions made a HUGE improvement.  I am embarrassed to say that I didn't even realize that normalization could be bumped up to "advanced".  Plus I did run the LNC 1st degree at 2 iterations.  Thank you so much for these instructions.  I have learned something.

 


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