2019 November: Complete LRGB Tutorial of NGC292, The Small Magellanic Cloud by Christian Sasse, Astronomer in Charge of iTelescope.net
2019 September: Astro Pixel Processor and iTelescope.net celebrate a new Partnership!
"Star Shaping" Rejection Filter?
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.
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 🙂 !
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.
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?
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 ?).