How is the Quality ...
 
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Poll results: What's a 'normal' score for your images?
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Poll is closed Mar 24, 2019
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How is the Quality Score calculated?  

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(@cheetah)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 28
21/03/2019 9:15 am  

My first clear night since October produced calibrated images with quality scores between 10 and 30.  Isn't this amazingly low??  I seem to recall my 'good' images being scored in the 400 to 500 range. 

I've made a few changes to my setup since my last session.  Did I miss something?  Or has the scoring system/values changed recently?  I'd love to know how it's calculated, so I can try to troubleshoot it better.

(Didn't find the info in the FAQ or a search, so perhaps others are wondering too.)


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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 2091
21/03/2019 11:00 am  
Posted by: Cheetah

My first clear night since October produced calibrated images with quality scores between 10 and 30.  Isn't this amazingly low??  I seem to recall my 'good' images being scored in the 400 to 500 range. 

I've made a few changes to my setup since my last session.  Did I miss something?  Or has the scoring system/values changed recently?  I'd love to know how it's calculated, so I can try to troubleshoot it better.

(Didn't find the info in the FAQ or a search, so perhaps others are wondering too.)

Hi @cheetah , perhaps you can share an image ?  So I can give you a proper answer. And please share the exact details of your optical setup (focal length, OTA etc..)

The quality scores are relative. There is no absolute score to indicate what a good score is actually.

The score is calculated with a special formula that consists of star density, noise and star shape.

Simply said, star density and star shape are relative in terms of imaging scale in pixels. If you register frames of different image scales, this will become clear.

In relative terms, frames with stars with a large FWHM value  in pixels will get a low score. But it does not mean that the frames are bad, it could simply mean that you are shooting with a very long focal lenght.

Later today I will try to update this post with the exact formula 😉

Kind regards,

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@cheetah)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 28
21/03/2019 2:49 pm  

Thanks for the quick reply!

I didn't finish the processing, since the scores are so low and I assumed there was a larger problem.  The .fit files are too large to attach, so I don't have a way to show you an image right now.

I'm shooting with an ASI1600mc-p, on a 6" newtonian 750mm, with a mpcc coma corrector.  Subs are 30 second unguided, from the edge of a small city.  Nearly a full moon, but no light hitting the OTA.

If the weather holds, I'm going to attempt the same target and will try guiding.  Maybe that makes more of a difference than I had thought...


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(@cheetah)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 28
24/03/2019 8:47 am  

I may have found the problem.  My OTA needed collimating...badly...  We'll see what happens with the next images I take.


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