M27 RC6 / OSC

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dx_ron
Posts: 35
Joined: Fri Apr 16, 2021 3:55 pm

M27 RC6 / OSC

Post by dx_ron »

M27_265x_38pctbin_Siril-color-weights_512k.jpg
M27_265x_38pctbin_Siril-color-weights_512k.jpg (504.49 KiB) Viewed 267 times
4.5 hours (265x60s) from my suburban backyard with the RC6 reduced to 993mm and QHY183C

After playing around with the colors a while, I went back to Siril (where I stacked) and ran the linear image through photometric color correction and then converted the values into ST scale (just inverted). I quite liked how that turned out, so I kept it.

astrobin link: https://astrob.in/opvj61/0/
Mike in Rancho
Posts: 541
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: M27 RC6 / OSC

Post by Mike in Rancho »

Nice detail. :thumbsup:

It strikes me as perhaps overall being just a wee bit blue shifted? Perhaps not. I would have to check out some kind of reference or look up some star spectrum numbers.

How does the scaling from Siril's photomathingy to ST work? I presume that when you run it, that the Siril on-screen log over on the right maybe gives some specs as to what the color channel adjustments were?

Since Ivo has said the channel bias sliders are just straight up linear multipliers (or dividers), I was wondering what scaling might be needed. I haven't run that Siril photo procedure in like a year, so I'll have to go try it again since I can't remember what it spits out.

The only caution I would have is that ST requires Wipe, of course, to set the channel floors against which the color sliders will then operate. I think. :think: And Siril, if operating on the original linear stack, would not have the advantage of that Wipe, unless similar pre-steps are performed?
dx_ron
Posts: 35
Joined: Fri Apr 16, 2021 3:55 pm

Re: M27 RC6 / OSC

Post by dx_ron »

Had time to go back and re-process the data to make a less-blue version.
The idea for using Siril's photometric weights was just to get a starting point, though when I set the values in ST I thought "that's pretty, I'll keep that".
The Siril weights, by the way, were R=0.583, G=0.411, B=1 so that was easy enough to express in ST slider terminology.

Anyway - here's the 'less blue':
M27_265x_38pctbin_pcc_less-blue.jpg
M27_265x_38pctbin_pcc_less-blue.jpg (481.8 KiB) Viewed 160 times

With reference to our discussion in my M39 thread - this RC6 + QHY183C image is way oversampled. Decon on the unbinned data left massive ringing, and it was far easier to keep things under control with bin-before-SVD.
dx_ron
Posts: 35
Joined: Fri Apr 16, 2021 3:55 pm

Re: M27 RC6 / OSC

Post by dx_ron »

Been flipping them back and forth on my monitor. I like the nebula better 'less blue', and the stars better 'more blue'. Maybe I will go back again to try to make both happen - clouds until at least Sunday here.
Mike in Rancho
Posts: 541
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: M27 RC6 / OSC

Post by Mike in Rancho »

Maybe somewhere in the middle? I'd have to look up the area in Stellarium to see the BV values of just how blue some of those stars are supposed to be.

But the M27 looks much improved. You can now see the red X in the center! :D
Stefan B
Posts: 225
Joined: Sat Oct 31, 2020 8:59 pm

Re: M27 RC6 / OSC

Post by Stefan B »

That's a great M 27! I prefer the second rendition but as Mike said, maybe somewhere between the two color balances?

I guess the data is broadband only? Given that, there's quite some detail in the nebula. :thumbsup:

Regards
Stefan
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