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Satelittes problem on stack  

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(@maciekja)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 3
May 13, 2020 18:07  

Hello everyone.

I have a question related to the settings to eliminate traces of satellites on the stack.

Do you have any experience with this? What settings are optimal? There is more and more of it and there is a growing problem with them.

Below 14 frames from last night, almost every track has a trace, sometimes even two 🙁

satelity

 


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2453
May 13, 2020 18:32  

Just sigma clipping, that is made for this. In 1.079 these settings are set automatically, if you use 20 or more frames, you will get the best rejection.


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(@maciekja)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 3
May 14, 2020 09:54  

What if I have less than 20 frames?
Sometimes, when I take supernova photos, I collect 10-15 frames. What will be the best manual settings then.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2453
May 15, 2020 20:25  

The automatic setting in APP 1.079 will already set the correct algorithm if you have less then 20 frames. Those will be working as well, just a bit less well as more data will always work better for detection of unwanted objects. If you deselect the automatic setting, you can choose the algorithms yourself and the tooltips will explain them then.


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(@maciekja)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 3
May 16, 2020 11:10  

I used automatic integration and settings as on the print screen.
Either way, the satellite tracks remain. Maybe I should change something in the LNC settings? MBB?
29 light frames were used for the stack.

APP1

 


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(@ralph)
Red Giant Customer
Joined: 1 year ago
Posts: 78
May 18, 2020 07:19  

I have been struggling with this as well.

@vincent-mod Is the outlier removal an iterative process? It seems that it's just a one-step process in the current implementation. A severe outlier (like a satellite trail) is detected and removed, but somehow the average of all data for that pixel value is still affected a bit. Adding an extra iteration to re-determine the average once more after outlier removal should make the process more robust, at the expense of computation time.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2453
May 18, 2020 17:01  
Posted by: @maciekja

I used automatic integration and settings as on the print screen.
Either way, the satellite tracks remain. Maybe I should change something in the LNC settings? MBB?
29 light frames were used for the stack.

Ok, interesting, I'd expect the automatic rejection to be a bit more effective, most likely when you have more data then. You can switch off auto and change to average integration. Then select "adaptive rejection" as the rejection filter and maybe set the kappa high to 2.5, you can experiment with that a bit (lower is more aggressive rejection).


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2453
May 18, 2020 17:03  

@ralph

The exact algorithm mechanics I don't know about (yet), working on that slowly. 😉 But like I mention above, it's likely the aggressiveness of the filter, which you can change by coming off of auto in this case.


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(@b4silio)
White Dwarf Customer
Joined: 2 years ago
Posts: 22
May 22, 2020 08:35  

Hi Ralph,

As a simple test, try to set the integration mode to "Median" and simply ignore the outlier rejection parameters. If you have your satellites streaks in less than half of the images then using the median should remove them entirely. The issue with using the average is that the streak is there to begin with (if for some reason it is not taken out by outlier rejection) and the other images are trying to average it down to the standard background level. With Median the streak will simply not be there at all, regardless of any outlier rejection applied.


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