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PostPosted: Tue Dec 27, 2011 4:40 pm 
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      The Flaming Star Nebula - click for an annotated thumbnail.
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The Flaming Star Nebula is actually just the bit at three o'clock (IC 405 on the annotated thumbnail) and a quick inspection shows how it got its name. The Tadpoles are associated with IC 410 and the web of hydrogen filaments gave rise to IC 417 getting the nickname The Spider. The Fly, not annotated, is the small (10 light years across) emission nebula, NGC1931, which lies roughly halfway between IC 417 and M36. The full resolution image (4096 x 3072 pixels) is available here but be aware that it's a 3.5MB download.

To give an idea of how much sky is visible one could fit roughly 25 full moons across the width of the image.

Shooting Information:
8 x 1000 seconds exposures of Hα to capture the nebulosity
5 x 200 seconds through each of Red, Green and Blue filters to capture the stars
3 x 1000 seconds through the Blue filter to see if there was any reflection nebulosity
Camera: FLI ML16803 cooled to -25°C.
Lens: 165mm focal length f/2.8 Pentax medium format
Pointing at: 5h 25m, +34° 30'

Processing was tough on this one as I was, as usual, scratching around close to the background noise for the faint bits. :evil:

Bob.

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Last edited by Bob Andersson on Tue Dec 27, 2011 7:49 pm, edited 1 time in total.

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PostPosted: Tue Dec 27, 2011 5:48 pm 
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WOW!! Not sure why you didn't get the bright reflection nebulosity in the Flaming star itself with 1,000 second blue subs - but I have not seen an image of this region showing the full extent of the emission nebulosity before. Impressive stuff!!
Greg

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PostPosted: Tue Dec 27, 2011 6:10 pm 
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Thanks Greg. I did pick up some reflection nebulosity but I didn't go deep enough to be comfortable about adding it in to the final image - my processing skills still have a long way to go. The small scale probably didn't help either. Might be a good target for the TEC 140 if it ever arrives! :roll:

Bob.

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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 Dec 27, 2011 7:07 pm 
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By the way - the dark splodges on IC410 are not the tadpoles - but that doesn't stop it from being a very interesting image :D
Greg

You can see the tadpoles at the 10 O'clock position on IC410 here:
http://blog.deepskycolors.com/archive/2 ... d-the.html

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http://www.newforestobservatory.com/
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PostPosted: Tue Dec 27, 2011 7:50 pm 
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Hmm, I prefer my version of the story but I've corrected the text... :lol:

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
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: Wed Dec 28, 2011 1:57 am 
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Nice work Bob!


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PostPosted: Wed Dec 28, 2011 12:14 pm 
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Hi Greg,

I spent a little more time looking at the imagery I captured through the Blue filter. Those 1,000 second exposures really bloat the brighter stars and make my normal star removal processing quite problematic but I did persevere for five small areas. By the time I had finished and added the result to the image I really wasn't seeing additional structure, just a slight colour cast to the brightest bits. For reference here's an animation of the area of the Flame Nebula at 100% from the image above alternating with my stacked (3 x 1,000 second) blue data. Relative brightness will not be correct and I haven't done any additional processing to enhance the blue nebulosity - just a quick and dirty comparison. At this scale there are differences if one looks carefully enough but they get totally lost when the image is resized.
    Image


@Gordon: Thanks Gordon. All contributions to help motivate me to spend another night out of bed are always welcome. :lol:

Bob.

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
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: Wed Dec 28, 2011 4:19 pm 
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Hi Bob,

Good to see the comparison. I'm not at all sure why the blue signal appears to be so low. Does the QE of your CCD die at the blue end?

Greg

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http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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PostPosted: Wed Dec 28, 2011 6:08 pm 
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Hi Greg,

Not hugely. Here's the response of the same chip in an Apogee body:
    Image
Kodak's data sheet is available here (PDF).

I wouldn't read too much into that comparison image except to notice that there are differences and that on the scale imposed by my 165mm focal length they aren't big in terms of how many pixels long they are. The Blue data is basically the 16 bit TIF file output by PixInsight stretched so that there is minimal clipping and then converted to 8 bit for web display and those differences could easily be emphasised with judicious processing. My problem arises from the size of the stars in that image as my chosen methodology is to remove the stars from any nebulosity images, process as seems fit and then add stars back from separate and much shallower RGB exposures which, because I have removed any nebulosity from them, can also be slightly deconvoluted without risk of ringing. I might be able to reduce the bright star sizes in those long blue subs by using shorter exposure times but then I'd need to stack a lot more subs to recover the nebulosity. I'm always up for suggestions provided they fit in with my star removal methodology but I am really wondering if there is much to gain given the image scale. I wouldn't be trying to capture the reflection nebula in the Pleiades with the 165mm lens so is there much point trying to do the same for the flame nebula with that lens?

Sorry, I've rambled on a bit with this reply and I've got a bit further to go. I justify (to myself) the huge boost in Hα luminosity relative to the surrounding RGB stars in my images so far because without it the stars would overwhelm the image for most subjects. Similarly, I justify a very non-linear stretch of the Hα data because the eye, not to mention the average computer monitor, couldn't easily accommodate the dynamic range. I've yet to get into narrowband imaging at wavelengths other than Hα but I know I'm not only going to have to employ similar tricks but also compromise still further by boosting the brightness of, say, OIII relative to Hα to prevent the Hα from totally overwhelming the OIII. And that's not even getting into what palette to use.

As I see it a similar problem exists when combining reflection nebulosity with narrowband Hα data. How to choose the relative brightness? If I reference the blue reflection nebulosity luminosity to the stars responsible for it then, because I choose dim stars relative to the Hα, you'd never see it. If I boost the reflection nebulosity luminosity so that it compares with the Hα then one ends up with what effectively is a false colour image. As you know, I play tricks with the Hα when I colourise as I allow more white through for the brightest bits but I'm not convinced about then adding blue to the mix for the reflection nebulosity. One either ends up with magenta or one arranges for the blue (or milky blue) to mask the red of the Hα to some degree. The former may be more honest but looks, to my jaundiced eye, rather odd while the latter isn't honest at all as there's little physical justification for it and I doubt it would even really work.

Forgive me. If your after dinner slurp of Christmas port hasn't sent you to sleep then this post will almost certainly do the trick! I've said nothing that you, as an experienced astrophotographer with some cracking imagery, won't have worked through years ago. I guess I've shared so you know where I'm coming from in my quest to combine disparate data in as honest a way as I can while still producing visually appealing results. I've not got many answers yet but I'll get there and hopefully I'll be happy with the results when I do...

Please keep the feedback coming as and when you feel so motivated. 8)

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
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: Wed Dec 28, 2011 7:31 pm 
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Steve Cannistra goes through how to deal properly with H-alpha OIII data here: http://www.starrywonders.com/bicolortechniquenew.html
Greg

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http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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PostPosted: Thu Dec 29, 2011 11:04 am 
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Hi Greg,

Thanks for the link: duly bookmarked for careful reading later.

After having spent some time on trying to extract the reflection nebulosity I did add it to the image so thanks for prodding me in that direction. At the scale of the entire image the change is very slight but one benefit of my choice to represent the brighter parts of the Hα as whiter has meant avoidance of too much magenta. My decisions on how much blue to add still feel very arbitrary and based more on aesthetics than science but the process has given me much food for thought and I'll look forward to refining it in the future.
    Image
Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
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 Dec 29, 2011 11:48 am 
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Impressive work Bob! The details in the gas clouds are outstanding!

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PostPosted: Thu Dec 29, 2011 7:12 pm 
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Amaizing image Bob!

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PostPosted: Mon Nov 19, 2012 5:32 pm 
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Hi folks,

Here's a reprocess of the original data. I think I'm getting better. :roll:

    Image

Bob.

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
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: Mon Nov 19, 2012 5:40 pm 
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I don't understand a thing about astrophotography, but this is just beautiful, good job :D

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