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PostPosted: Tue Mar 20, 2012 3:18 pm 
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Hi folks,

Having never set out to image a distant galaxy before I thought "Why stop at one?"

    Image
This is (most of) Markarian's Chain - field of view is about 2┬░across. Frustratingly the cloud rolled in at about 1:30 last night so I was only able to get 6 x 1,000 second unguided subs through a red filter and looking at the raw data, while I'm pleased with what I was able to achieve at f/7, there's certainly scope for improving the signal to noise ratio as that would allow me to show more of the extended nebulosity that I can see in that data. This is very much a preliminary go at post-processing but I thought I'd share - hopefully green and blue will follow in the days to come, weather and Moon permitting, and then I can spend some time trying to hone my skills as I'm already finding that what works for processing narrowband imagery doesn't always translate.

Bob.

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OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
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PostPosted: Sat Mar 24, 2012 7:06 pm 
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Hi folks,

Wow but this deep sky stuff is difficult! I didn't do myself any favours as the green and blue subs were all taken with the camera inadvertently rotated by 9┬░ from where it should have been. Amazingly PixInsight can actually cope with this but one is left with a choice either to crop or to be a little more inventive. So, to get the boring stuff out of the way first, I had 12 red subs and 8 each of green and blue, all taken with a 1,000 second exposure time for a total exposure time of a little under eight hours! I combined the lot to obtain a synthetic luminance image and combined the reds, greens and blues separately to obtain, yes - you've guessed it, red, green and blue images. Those were combined to obtain an RGB image. That had to be cropped and rotated to match the luminance image and PixInsight's LRGB tool was used to add colour to the luminance image, though obviously that colour couldn't extend everywhere! Frankly I wasn't very happy with the overall colour balance so I toned it down both at the combination stage and during subsequent processing in Photoshop. There are artefacts around the edges of the frame due to that camera rotation but I've chosen to include the whole frame as the alternative would have been to crop out some interesting stuff. With more time than I have available I guess I could airbrush out the defects without destroying the integrity of the image but one thing I have discovered is that capturing and processing galaxy images is much harder than I thought it would be!

    Image
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: Sat Mar 24, 2012 7:39 pm 
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You remind me I should be out more while we have clear(ish) skies, although its not quite clear enough recently for me to be motivated.

On PixInsight's registration abilities, I can confirm it works great having given it a bigger stress test recently. Long story short, I tried to mix 450D and 600D data, and sure enough, it successfully scaled them accordingly. Even more interesting, I used a SII frame as reference, and found the OIII and Ha to be scaled 0.994 and 1.004 not necessarily in that order. It might be too easy to blame this on lateral CA, given SII and Ha are so close together, so maybe it's focus or even a distortion effect as I didn't get the subject placed exactly each set!

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PostPosted: Sat Mar 24, 2012 7:48 pm 
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It's full of stars!...err, galaxies! :mrgreen:

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PostPosted: Sun Mar 25, 2012 9:19 am 
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@eVolutioN: Nice reference to "2001: A Space Odyssey" there. 8)

@popo: I know exactly what you mean. The light meter on the roof suggested that about 25% of the incoming was blocked by the haze yesterday. The alignment tool I used for the LRGB combination was the DynamicAlignment tool which was new to me. As usual I had originally aligned the stack using the StarAlignment tool but when I cropped the colour combined RGB images to remove the bad sections caused by that inadvertent camera rotation the image alignment was lost. DynamicAlignment came to the rescue - the whole procedure is described in Harry's video tutorial here. The more I use PixInsight the more in awe of it I become!

BTW, I've done a little extra clean up of the image above. Still some artefacts but you have to look a little closer to see them now.

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: Sun Mar 25, 2012 10:40 am 
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Ok, so that's what the light meter is for? I was wondering... I just use the low tech eye test. Last night was pretty awful. Orange hue from light pollution was visible to the eye to beyond 45 degrees up. Even above that, I could count the visible stars on one hand.

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Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
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PostPosted: Wed Mar 28, 2012 2:54 pm 
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Lovely, I havent tried this part of the sky yet, I wonder what would show up on my 250p DS with DSLR.

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PostPosted: Tue Jan 29, 2013 6:31 pm 
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Hi folks,

Having been hard at work developing a PixInsight script (Repaired HSV Separation) which allows me to bring out the faint stuff without losing most of the colour I thought I'd update this thread.

    Image

Same data as before but now I'm learning how to get the most from it! The image is a composite of a "regular" stretch and a stretch of the V component of an HSV separation

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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