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Odd stars with Starnet++

Nikita Misiura StarNet Supernova Remnant Artifacts
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George Hatfield avatar
George Hatfield avatar
I've been working on some image data for the Vela SNR, which dates from 2017.   I used Starnet++ to remove the stars from the linear RGB image.  The starless image was fine, but the star image had red bars in some of the stars.  See the attached.  This is only apparent at 100%, but I'd like to find the cause and prevent it if I can.  Has anyone seen this?  Cause?

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andrea tasselli avatar
andrea tasselli avatar
Have you done anything to it, such as drizzle 2x? What parameters for SN++ and what SN++?
George Hatfield avatar
George Hatfield avatar
Andrea…  Thanks for the question.  It is not Starnet++ that is creating the problem.  I went back and looked at the R, G and B masters and the problem is there.

George
andrea tasselli avatar
andrea tasselli avatar
George Hatfield:
Andrea...  Thanks for the question.  It is not Starnet++ that is creating the problem.  I went back and looked at the R, G and B masters and the problem is there.

George

The seems more in tune with my experience with SN++. Glad you found the source of the issue.
Brian Puhl avatar
Brian Puhl avatar
George,

That's bad rejection.   I actually experienced this the other day when stacking data between 2 and 3 scopes.   We saw that sort of artifacting present when we used Winsorized rejection.    Once we switched to ESD (Extreme Studentized Deviate), all of our issues went away.      Give it a shot.

-Brian
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George Hatfield avatar
George Hatfield avatar
Brian…  thanks for the idea.  I tried it (ESD) and got the same result.  I think the problem is that many of the green subs have very poor eccentricity (>0.8) and this makes stacking by any method difficult.  The red and blue are OK.  What is the saying about making a "silk purse?"  Time to move on to the next data set. 
George
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Brian Puhl avatar
Brian Puhl avatar
George Hatfield:
Brian...  thanks for the idea.  I tried it (ESD) and got the same result.  I think the problem is that many of the green subs have very poor eccentricity (>0.8) and this makes stacking by any method difficult.  The red and blue are OK.  What is the saying about making a "silk purse?"  Time to move on to the next data set. 
George




Makes sense.   That's a bummer.   You could TRY batch processing the data set with BlurX, use an ImageContainer and run all the individual subs through it.    I've only tried this once, but maybe.      Just a thought, but I'd understand if you moved on.
George Hatfield avatar
George Hatfield avatar
I tried running BlurX on one of the poorer green subs.  The result was smaller elongated stars.  Not much help.  I reduced the final image in half (resampled), and the star problems are hard to see so that is what I will use.   Here is the hopefully, final image:  https://www.astrobin.com/urcg7u/

George