The issue I’m facing is CA in my final stack. Lateral I think. I’m wondering if wbpp is allowing too much variation in star size and eccentricity with it’s default settings. I REALLY don’t want to blink through 300 or more subs.
is there a way to tell wbpp to only use the best stars?
thx in advance!
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If it's all stars in the same direction you can use the Channel Match tool and correct both the x and y directions.
Mike
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Sean Mc:
is there a way to tell wbpp to only use the best stars?
In the Lights tab under Subframe Weighting you can select Weighting Formula and set your own weights for how much each parameter should carry. You could increase the weight given to FWHM and Eccentricity there.
Or you could also just use Subframe Selector to filter out substandard subframes before even running WBPP.
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Well. My 5C…
WBPP is a splendid tool, but as is true anywhere else: 💩in, 💩 out.
Blink is tedious and not objective. That’s where subframe selector comes in. FWHM is the value I am looking at when focus or air turbulence is an issue. Under these circumstances I am often throwing out 60% of frames, or more…
hobby for masochists…
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In general, there is too much focus on eccentricity when it comes to culling and manual weighting.
If your FWHM is good, your eccentricity is almost always going to be less than great. There's almost an inverse-relationship. Want a great eccentricity metric? It's easy... just defocus into a nice, round disc.
My best subs (where the FWHM gets down to around 2") always have moderately high eccentricity. The sharper your stars get, the harder it is to keep them round. But there is enough variation between frames that this all gets averaged away by stacking.
A sub with a high FWHM is unlikely to be of value. A sub with a high eccentricity may be some of your best data.
I just look at FWHM and star count when culling via SubframeSelector. FWHM outliers go. Those subs with aberrant star counts get a closer look to see if there has been a problem (e.g. clouds). Then WBPP can deal with the rest.
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Aaron H.:
In general, there is too much focus on eccentricity when it comes to culling and manual weighting.
If your FWHM is good, your eccentricity is almost always going to be less than great. There's almost an inverse-relationship. Want a great eccentricity metric? It's easy... just defocus into a nice, round disc.
My best subs (where the FWHM gets down to around 2") always have moderately high eccentricity. The sharper your stars get, the harder it is to keep them round. But there is enough variation between frames that this all gets averaged away by stacking.
A sub with a high FWHM is unlikely to be of value. A sub with a high eccentricity may be some of your best data.
I just look at FWHM and star count when culling via SubframeSelector. FWHM outliers go. Those subs with aberrant star counts get a closer look to see if there has been a problem (e.g. clouds). Then WBPP can deal with the rest.
absolutely agree.
might add that you can skip the step of giving eccentricity a closer look: BlurX "Correction only" does a FANTASTIC job in getting you sweet round stars. all the way to the corners...
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Hmm. Yeah I thought my previous Ha stack was the best of the group, but a quick try with sfs culled 60% of my Ha. Probably due to my eccentricity setting. I would have thought that eccentricity was what was causing the CA in my combined lights (due to the atmosphere)
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Michael Gruenwald:
Aaron H.:
In general, there is too much focus on eccentricity when it comes to culling and manual weighting.
If your FWHM is good, your eccentricity is almost always going to be less than great. There's almost an inverse-relationship. Want a great eccentricity metric? It's easy... just defocus into a nice, round disc.
My best subs (where the FWHM gets down to around 2") always have moderately high eccentricity. The sharper your stars get, the harder it is to keep them round. But there is enough variation between frames that this all gets averaged away by stacking.
A sub with a high FWHM is unlikely to be of value. A sub with a high eccentricity may be some of your best data.
I just look at FWHM and star count when culling via SubframeSelector. FWHM outliers go. Those subs with aberrant star counts get a closer look to see if there has been a problem (e.g. clouds). Then WBPP can deal with the rest.
absolutely agree.
might add that you can skip the step of giving eccentricity a closer look: BlurX "Correction only" does a FANTASTIC job in getting you sweet round stars. all the way to the corners...
BlurX doesn’t seem to want to get rid of the fringing i’m seeing for some reason. The stars are nice and round. It’s just the largest stars all have a different color on top and bottom. I thought it was alignment, but I tried manually aligning the narrowband stacks and it didn’t help either.
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Sean Mc:
Hmm. Yeah I thought my previous Ha stack was the best of the group, but a quick try with sfs culled 60% of my Ha. Probably due to my eccentricity setting. I would have thought that eccentricity was what was causing the CA in my combined lights (due to the atmosphere)
Hi Sean, you have to set in SFS the threshold of FWHM case by case, do not work with default.
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Yeah, I did. I set the cutoff to the top of the light grey area. Turns out my Ha subs were averaging over 2.3 and my OIII and SII were averaging 1.4?!?
Anyway, after culling everything, my combined rgb still has the fringing so I’m at a loss for how to fix it.
The fringing is only on the largest stars. All of the small ones seem fine.
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Interesting. I tried the channel match tool, and it’s possible to remove the fringing on the largest stars.
of course all the other stars are WAY out now lol.
i can’t win!
Any other ideas?
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ChannelMatch is a well kept PI secret, I find it an excellent tool, specially when you are low on the horizon, and the atmospheric aberration makes its diffraction job, by shifting the channels, specially with a color camera. But, as you point out, a single field translation applies to the whole image.
If you instead need to correct local aberrations, that happens frequently, the first and easiest tool that comes to my mind is, as @Michael Gruenwald stated above, BlurXterminator (BX). BX applies a local correction, specially effective with the latest AI update, released a couple of months ago.
If you are working with a monochromatic camera, I think you have to assemble the three channels together in a color image and apply BX, in order to get the alignment.
Hope this helps!
Ciao, Mau
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