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Taurus widefield - Problems with LPC  

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(@skanker)
Red Giant Customer
Joined: 2 years ago
Posts: 70
January 16, 2021 16:03  

Hello from Austria!

 

My stack shows a strong gradient and i don't get a proper correction in the tool.

Taurus 105mm St

 

I uploaded the stack for you: https://drive.google.com/drive/folders/1PRxmRdlqNGAdA47VoR4w83qEz6rgTTiX?usp=sharing

Is the material unusable?

 

CS Gernot

 


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(@wvreeven)
Galaxy Admin
Joined: 2 years ago
Posts: 586
January 17, 2021 13:22  

@skanker Ouch that is a nasty gradient. I am downloading the file right now to see what I can do with it.


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(@wvreeven)
Galaxy Admin
Joined: 2 years ago
Posts: 586
January 17, 2021 13:28  

@skanker Whatever I try, I keep on getting strange artifacts at the bottom of the image. Did you process each individual panel before combining them to the mosaic and, if yes, what did you do?


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3058
January 17, 2021 14:41  

I had a look as well and the trick here is to gradually set Light pollution correction boxes on the edges of more extreme gradients. I started with 5 around the edges and slowly adding more and checking what APP makes of it. There is quite a lot of gradients, both due to light pollution but also in color. So I creeped up onto the patches of color as well as dark and light spots. To make everything as visible for me as possible, I cranked up the saturation and stretched to the max (as you want to avoid background nebulosity as much as possible). Like so;

Phase1

Setting the saturation and stretch back to a more normal level shows this;

Phase2

And this is the background model APP calculated, it looks nice and gradual, also indicating the model is likely to be correct;

LPC Model

If you get this, save that as fits and then you can reload and try to make it even a bit better by doing the same. And then stretching more also makes for a nicer image.


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(@skanker)
Red Giant Customer
Joined: 2 years ago
Posts: 70
January 17, 2021 15:10  

@wvreeven

First thanks for your help Wouter. It is not a mosaic but a single image (180x60sec.).

The black border was probably caused by the clip filter (Optolong L-Pro).

 

@vincent-mod

Also thanks for your help Vincent. That should be LPC on the highest level 🙂

I always take pictures in my garden but i have never had such gradients. Do you have any idea where these spots of color could come from?

 

CS

 

Gernot


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(@wvreeven)
Galaxy Admin
Joined: 2 years ago
Posts: 586
January 17, 2021 15:14  

@skanker A sorry, I seemed to have remembered that it was a mosaic but clearly I was wrong. Great pic by the way!


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3058
January 17, 2021 15:37  

@skanker

Thanks! Well to me this looks like you had a light source in the corner. The model APP calculated (that 3rd picture above) is a likely good representation as to where that source came from. Maybe a light of the neighbors or a bit more in the distance on that side? The color patches, I'm not an expert in why those become stronger, but I can imagine this to also happen with light pollution and an RGB sensor.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3058
January 17, 2021 15:58  

I had a bit of extra play with post processing, correcting the colors a little, adding a bit of contrast, minor crop of the edges etc. It's definitely nice data for just 60 second exposures!

Taurus 105mm lpc cbg mod St

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(@skanker)
Red Giant Customer
Joined: 2 years ago
Posts: 70
January 18, 2021 07:48  

@vincent-mod

Thank you for your efforts Vincent! Your input helped me a lot. I will post my results here in the next few days 🙂

 

CS

 

Gernot 


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(@skanker)
Red Giant Customer
Joined: 2 years ago
Posts: 70
January 31, 2021 15:57  

Hello @Vincent-mod & @wvreeven

 

Here is my final (!?) result:

Taurus Web

 

Full resolution and infos can be found here: https://www.astrobin.com/1c0jx0/?nc=user

I look forward to your feedback 🙂

 

CS

 

Gernot 

 


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(@wvreeven)
Galaxy Admin
Joined: 2 years ago
Posts: 586
January 31, 2021 16:11  

That is a stunning image. Congratulation!


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3058
January 31, 2021 21:07  

Very nice, great detail you got out of the background! Maybe a bit bright on the 7 sisters?


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(@skanker)
Red Giant Customer
Joined: 2 years ago
Posts: 70
February 2, 2021 12:52  

@vincent-mod

Thx 🙂 Its not the final version of the picture ! I will collect a bit more feedback and then work it into the picture.

CS

Gernot 


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