"Star Shaping" Reje...
 
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The problem with the data upload limit for attachments has been fixed. I have restored it to 30MegaBytes. A recent forum software upgrade was responsible for the changed limit. Please accept my apologies for missing this when upgrading the forum sofware, Mabula.

"Star Shaping" Rejection Filter?  

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(@rowland-f-archer-jr)
Red Giant Customer
Joined: 2 years ago
Posts: 70
28/03/2019 12:29 pm  

Hi Mabula,

I'm currently fighting with a star shape problem in my frames (prior to processing them - it's in the "raw" FITS frames from the ASI1600MM on my 120mm refractor).  It sort of looks like coma distortion - a fan shaped "tail" on the stars.

I'm correcting this in post-processing, but it occurred to me that during the analysis phase, APP knows where the stars are, and during integration, it rejects outlier pixels.  Would it be possible to reject pixels that fall outside of a circular region centered on the star's centroid?  I suppose some people may consider this "painting," but since stars are all round, it is a form of correction for optical distortion.  

I think this would be a very useful, if perhaps controversial, feature!  We all want nice round stars in our images.

Cheers,
Rowland

This topic was modified 5 months ago by Vincent Groenewold - Moderator

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(@vincent-mod)
Galaxy Moderator
Joined: 2 years ago
Posts: 596
04/04/2019 11:22 am  

That might be possible I guess, a bit like what other apps do with a script of some sort. I guess something like this might be possible in the future when Mabula starts working on more post-processing options.


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(@rowland-f-archer-jr)
Red Giant Customer
Joined: 2 years ago
Posts: 70
04/04/2019 11:39 am  

Hi Vincent,

Thanks for your reply.  It's definitely possible in post-processing.  It seemed to me it was possible in pre-processing and might be more effective there.

I agree it is a more "advanced" feature, but it could be a distinguishing one if it ended up working better before the stretch.  People spend a lot of effort trying to get nice round, tight stars and as a friend of mine said, "anything that puts the pixels back where they belong" is a big help 🙂 !

Cheers,

Rowland


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(@vincent-mod)
Galaxy Moderator
Joined: 2 years ago
Posts: 596
04/04/2019 12:19 pm  

Haha yes I agree, but at the same time it shouldn't affect the surrounding data too much, which is tricky I think. I do like deconvolution in PI for instance, some see that as "making up data", but it really isn't and when used on proper data it can be amazing. The rounding of stars usually degrades the data a bit it seems, in those cases I'm not a big fan of it and I just take-away I need better data. 🙂 I think it could definitely be an interesting option though.


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(@rowland-f-archer-jr)
Red Giant Customer
Joined: 2 years ago
Posts: 70
04/04/2019 2:00 pm  

You are right, better data is the best answer!  Deconvolution is mathematically-based and we know it is essentially undoing blurred data so I agree with you, I don't view it as "making up data."  

And yes, artifacts around stars definitely can result from shrinking the stars in later processing stages.  That's actually what led me to think about doing it early - we need some Mabula Magic (tm) :).  Some form of local normalization around the star?   


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(@vincent-mod)
Galaxy Moderator
Joined: 2 years ago
Posts: 596
12/04/2019 9:39 am  

Ha! Mabula Magic, very good idea to put that in the feature list. 😉 Yes, he's the mathematics wizard so maybe there is a way (@mabula-admin ?).


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