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How to get rid of strange gradient in 3-image mosaic  

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(@tailspin45)
White Dwarf Customer
Joined: 10 months ago
Posts: 19
July 15, 2021 21:54  

Tried building this mosaic with MBB set at 15%, but you can see the result in the heavily stretched image. Currently trudging through same integration with 40%

273 frames 4144  x  2822, three sessions. ASI294MX Pro gain 120, 120-second exposure with cooling at -10ºC

Can anyone suggest the source of the gradient or, better yet, how to get rid of it?

Astro Pixel Processor version 1 083 beta1 © Aries Productions

 

This topic was modified 2 months ago by Tom Harnish

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(@vincent-mod)
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July 18, 2021 12:45  

Did you use LNC as well?


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(@tailspin45)
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Joined: 10 months ago
Posts: 19
July 18, 2021 14:45  

@vincent-mod  Yes. 1st degree with 3 iterations


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(@vincent-mod)
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July 19, 2021 08:56  

Mmm, could you show a screenshot of the integrations per session? So what the separate panels look like?


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(@tailspin45)
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Posts: 19
July 19, 2021 17:12  

Stacks of session 1, 2, and 3

 

Cygnus session 1
Cygnus session 2
Cygnus session 3
This post was modified 2 months ago 3 times by Tom Harnish

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(@vincent-mod)
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July 20, 2021 11:27  

Mm, not much to see really. Could you upload like 5 subs per panel to our server, so I can try as well?

Go to https://upload.astropixelprocessor.com and use upload as username and upload as password.

Create a directory named “tailspin45-mosaicissue” and upload in there. Thank you!


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(@tailspin45)
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Joined: 10 months ago
Posts: 19
July 20, 2021 17:36  

@vincent-mod Done. Created three subfolders, one for each session, with the requested 5 subframes for each session.

This post was modified 2 months ago by Tom Harnish

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(@vincent-mod)
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July 20, 2021 17:42  

Thanks! I forgot to ask, but could you also upload master calibration data to the same folder?


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(@tailspin45)
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July 20, 2021 21:04  

@vincent-mod Done. Master dark and master flat, didn't make or use a master dark-flat

 


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(@vincent-mod)
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July 21, 2021 15:46  

Thanks Tom, give me a day to process. Bit busy at the moment, sorry.


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(@vincent-mod)
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July 23, 2021 17:23  

Sorry, took a bit longer. So I was confused as I got a 2 panel result. But it seems you accidentally uploaded the same data across 2 sessions. 🙂


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(@tailspin45)
White Dwarf Customer
Joined: 10 months ago
Posts: 19
July 23, 2021 19:18  

You're right. Session 1 files are now the proper ones.

This post was modified 2 months ago 2 times by Tom Harnish

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(@vincent-mod)
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July 23, 2021 19:56  

Thanks Tom, I'll work on it this weekend and come back to you then.


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(@vincent-mod)
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July 25, 2021 15:49  

Hi Tom, so I had a go with the mosaic. First without calibration data (as that can be a cause of many issues).

I used mosaic integration, advanced normalization, scale stop to 10, LNC and MBB at 20% (there is a lot of overlap, so much that it's almost not a mosaic actually).

First result;

mosaic

Clearly a lot of light pollution, so I'll try your flats after this.

Light pollution correction, going from the outside-in with the boxes;

mosaic corrected

And without all those boxes;

mosaic corrected lpc

I added some saturation, with higher contrast as well. Seems to work, though could be better, let me try with some calibration data.


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(@vincent-mod)
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July 25, 2021 16:07  

Ok, now with flats, they did help a bit, but you seem to have quite a lot of light pollution issues over there unfortunately. I think correcting the panels first nicely and then making the mosaic will work better. Now I just cropped a part that wasn't behaving nicely, it's still ok, but if we could manage the pollution better that would help a lot.

mosaic test crop

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(@tailspin45)
White Dwarf Customer
Joined: 10 months ago
Posts: 19
July 25, 2021 18:31  

Thanks for your efforts. they certainly turned out better than mine!.

I live in a Bortle 7-8 area and try to manage light pollution with an Optolonhg L-Pro filter.

But the bigger issue may be local incident light from a street light across the street and bright lights at a desalinization plant about 1500m away.

Again, thanks for your help!


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(@vincent-mod)
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July 25, 2021 19:16  

Oeh yeah that's not very nice indeed. I would also look into using narrow-band filters, that will help a lot in your situation. Have a look at a nice H-alpha filter, maybe you can borrow one from someone?

Is my above answer helping you to get the same result? That would be great if so. 🙂


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(@tailspin45)
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Joined: 10 months ago
Posts: 19
August 5, 2021 00:44  

@vincent-mod Just to wind up the topic here, I've hung a black curtain to block the nearby light sources, and have invested in an L-eXtreme narrowband filter.

Results so far look promising. Case closed, I say, and thanks for the help.

I'll post an image here if, indeed, the problem is solved.


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(@vincent-mod)
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August 7, 2021 13:46  

That's great to hear Tom! If you need any help processing that kind of data, let us know!


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(@tailspin45)
White Dwarf Customer
Joined: 10 months ago
Posts: 19
August 13, 2021 20:46  

Rotated 90º

Cygnus Wall HST V22 AI
This post was modified 1 month ago by Tom Harnish

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