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turning off LNC, can't get sample size


(@mrrat)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

1419 - 6) INTEGRATE: integrate light frames: LNC: starting Local Normalization Correction...
1419 - 6) INTEGRATE: integrate light frames: LNC: turning off LNC, can't get sample size

What would cause this?


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(@vincent-mod)
Universe Admin
Joined: 5 years ago
Posts: 5130
 

Ok, so this can be a number of things;

- The number of frames you're trying it on is too low (how many are you using, how much overlap do they have?)
- The LNC setting, how did you set that (at what value?)
- The number of frames is so high, the calculation becomes too complex, which is not yet possible (like when using 10000 frames or something like that).

Thanks, Vincent


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(@mrrat)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

@vincent-mod  thanks

Mosaic with 1600 frames over 10 sessions 🙂
I'm currently using a small tracker so exposure times are short. Waiting on my Losmandy mount to be built so I can get some decent exposure times.

 


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(@vincent-mod)
Universe Admin
Joined: 5 years ago
Posts: 5130
 

Ah yes that's likely it then. You can also make sets of your data, so first integrate 1 panel then the next etc. and only after all panels are done, you make the mosaic. That will likely work for LNC.


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(@mrrat)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

APP ran for a week and the result was unusable without the LNC.  Ran each session separately and then combined and that only took a couple days and the results are great.

Did run out of memory attempting star reduction on the 1.2GB fits file with 26GB RAM dedicated to APP. 
Running the tiff through Starnet++ instead.


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(@vincent-mod)
Universe Admin
Joined: 5 years ago
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Excellent to hear Steven! Bit unfortunate for the reduction, Mabula is working on also getting the load on the system better with this module.


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(@safinsd)
White Dwarf Customer
Joined: 1 year ago
Posts: 20
 

@vincent-mod I just got the "turning off LNC, can't get sample size" on an integration of 5,215 lights. I hate to stop the integration at 49%, but should I? Will the result be unusable? Also, what is the max number of lights I should try to integrate?


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(@vincent-mod)
Universe Admin
Joined: 5 years ago
Posts: 5130
 

Sorry for the delay, bit busy down here. Over 5000 lights is maybe a bit much to do at once, I would combine data in such a case, like going for the integration of 500 at a time and then combining those results with each other.


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(@safinsd)
White Dwarf Customer
Joined: 1 year ago
Posts: 20
 

I understand. Thank you for getting back to me. Amazingly, the stack completed in about 60 hours and the result was fine. 


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(@jochen-scharmann)
Main Sequence Star Customer
Joined: 3 years ago
Posts: 72
 

Hi @Susan Fortney

The max amount of Lights is heavily depending on Your hardware, especially RAM (size & speed) and CPU performance. I have successfully processed up to 700 lights with 24GB of DDR3 RAM.

Also the degree number of LNC isinfluencing RAM requirement / processing time strongly. Try to start with 1st degree (maybe just 100 lights) and watch the console to get a feeling how long it takes for 1 iteration to go. Running 700 lights or more on 2nd degree with 3 iterations is an overnite job (give it 8-10 hours or so), so You should make sure all other adjustments are great before trying LNC (which should be just icing on the cake for normal shots).

As a rule of thumb, with each degree step, calculation time increases by a factor of around 400% for each iteration.

You also need to be aware of disk space as APP requires several 100 GB as swap memory to push and pull data from. Therefore a fast SSD should be used here Increasing number of lights will also eat that swap memory faster, so clean Your Disk (or use a fast external) for such job. Once You see the HDD indiator in red territory for too long, APP is likely unable to continue the job successfully.

Please note, LNC is a single-core code, hence depending on the single core CPU performance only - A recent INTEL or Apple Silicon based machine really helps. Apparently multi-core/thread code is in the works which might speed this up in future APP versions.

Hope this helps, Clear Skies

Jochen


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