Author Topic: M83 (Southern Pinwheel)  (Read 2274 times)

Offline Geoff

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M83 (Southern Pinwheel)
« on: 2014 May 01 21:27:26 »
This is one which (I think) looks good at first glance, but faults show up on closer inspection:
  • Some sort of ringing artifacts in the bright stars
  • A red fringe on one side of the brighter stars.  This one really has me puzzled.  It looks like a registration error, but registration was done in PI, so it can't be wrong (or can it?)  I also did the registration twice as a check on possible user error.
http://www.astrobin.com/93786/
Geoff
« Last Edit: 2014 May 01 21:38:30 by Geoff »
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Offline Juan Conejero

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Re: M83 (Southern Pinwheel)
« Reply #1 on: 2014 May 02 01:45:18 »
Anything can go wrong, anywhere, anytime, but judging from your picture, registration is spot-on on the whole image. I know this because the diffraction spikes don't move when I cycle through the red, green and blue channels using the channel selector and the mouse wheel. So I'm afraid this is a hardware problem...
Juan Conejero
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Offline Geoff

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Re: M83 (Southern Pinwheel)
« Reply #2 on: 2014 May 02 02:20:18 »
Anything can go wrong, anywhere, anytime, but judging from your picture, registration is spot-on on the whole image. I know this because the diffraction spikes don't move when I cycle through the red, green and blue channels using the channel selector and the mouse wheel. So I'm afraid this is a hardware problem...
Thanks Juan
Do you have any suggestions as to what the hardware problem may be? I've done lots of images and this is the first time I've seen this problem.
Geoff
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Offline Alejandro Tombolini

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Re: M83 (Southern Pinwheel)
« Reply #3 on: 2014 May 02 09:54:06 »
Hi Geoff, maybe you can analize the original L, R, G, B images.

You have mentioned clouds, it could have generated biggest halos in some filter, but I am inclined by another cause. It also could have been generated during the processes. The background has chrominance noise spots (big ones) that easily affect the stars halos. 
If you have saved the project, see what happened after apply noise reduction.

Saludos, Alejandro.

Offline Geoff

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Re: M83 (Southern Pinwheel)
« Reply #4 on: 2014 May 02 15:24:27 »
Thanks Alejandro.  I'll follow up your suggestions.  I also think this thread http://pixinsight.com/forum/index.php?topic=6639.0
may be useful in dealing with the artifacts in the bright (saturated?) stars.
Geoff
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Offline lucchett

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Re: M83 (Southern Pinwheel)
« Reply #5 on: 2014 May 03 11:33:37 »
Geoff, did you try a RGB only?
Can you post a crop of one of the star in full res?
Andrea


Offline Geoff

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Re: M83 (Southern Pinwheel)
« Reply #6 on: 2014 May 03 14:52:09 »
Geoff, did you try a RGB only?
Can you post a crop of one of the star in full res?
Andrea
Will do Andrea when I get home after the weekend.
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Offline Physicist13

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Re: M83 (Southern Pinwheel)
« Reply #7 on: 2014 May 13 00:38:24 »
lovely! I've seen the red fringing on side before...not completely sure but my suspicion is that, the red will always have a larger spot size due to its longer wavelength so the R channe stars should, in theory, be shrunk slightly to match the GB channels. Also the one sidedness could indicate a sligtly non flat focal plance...which cld be due to filter tilt, camera chip tilt etc..
Patrick