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PostPosted: Tue Jan 17, 2012 5:11 pm 
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Hi folks,

With some spare imaging time left over on the previous two nights after Orion disappeared from view I had a crack at NGC 7822 which lies roughly halfway between the constellations Cassiopeia and Cepheus. Here's the result - south is down:
    Image
The nebulosity visible is entirely from the Hydrogen alpha emission line and the stars were added in from a separate set of RGB exposures.

This one had me scratching my head a bit when I saw the naked Hα image as I knew the ring couldn't be lens flare. Here was the puzzle: it's near the bottom of the image above, just to the right of centre and it looks like this (50% crop) with the stars turned down a bit:
    Image
It took me the best part of two hours to track this down and it's called Abell 85 (or CTB 1 if you prefer). There's a brief description of it here.

The main subject NGC 7822 is worth closer inspection and you can read more about it here.
    Image
Bob.

5 x 1500 seconds Hα (Astrodon 3nm)
5 x 200 seconds in each of R, G and B (Astrodon Tru-Balance)
Camera: ML16803
Lens: Pentax 6x7 MF 165mm at f/2.8
Target: 00h 05m, +67° 14'
Processed in PixInsight and PhotoShop

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OM-D E-M1 + ED 12-40mm f/2.8, H-F007014E, M.ZUIKO DIGITAL 45mm 1:1.8, M.ZUIKO DIGITAL ED 75mm 1:1.8, L-RS014150E.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Tue Jan 17, 2012 6:17 pm 
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Damn nice... in bigger picture, as well as close ups. I might not have even spotted that as being interesting with so much else going on.

I wonder if the sky ID tool I linked previously would have shown you what the then mystery object was?

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PostPosted: Wed Jan 18, 2012 10:14 am 
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.
Hmm. I've had a report from one source that the image looks clipped on some browsers. There is some slight clipping (spots rather than large areas) which seems to have occurred during conversion to JPEG but I've seen a much more serious effect on Safari (Mac OS) so maybe I've been too aggressive with the colour gamut... :oops:

But it looks just fine (to my eyes) in PhotoShop...

Update: I've reprocessed the first image to avoid the gamut problem induced, as it turns out, by PhotoShop's Shadows/Highlights tool when I attempted to show a little more highlights detail. Here's the result:
    Image
Has that got rid of the clipped appearance, assuming you were seeing it before?

Bob.

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OM-D E-M1 + ED 12-40mm f/2.8, H-F007014E, M.ZUIKO DIGITAL 45mm 1:1.8, M.ZUIKO DIGITAL ED 75mm 1:1.8, L-RS014150E.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Thu Jan 19, 2012 2:07 pm 
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Hi folks,

I've really struggled with the image above and I think I know why: the monochrome nebulosity image that I started with was too light and had too much of the faint background (borderline stuff as it was very near the noise threshold). I thought I could tune it later after I added the colour but every attempt to do so was causing other issues, most notably a gamut problem.

I'm still a long way down the learning curve on processing but rather than retreat into my shell until the next time I hope it is useful if I share my mistakes. So this morning I went back and coaxed the monochrome image much closer to where I wanted it before adding colour and adding back the stars and came up with this:
    Image
A little less "in your face" than the previous efforts and certainly a loss of some of the fainter nebulosity but I've got more detail in NGC 7822 while retaining Abell 85 so I think it's improved. Do you agree?

Bob.

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OM-D E-M1 + ED 12-40mm f/2.8, H-F007014E, M.ZUIKO DIGITAL 45mm 1:1.8, M.ZUIKO DIGITAL ED 75mm 1:1.8, L-RS014150E.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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