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 Post subject: The Heart - Fire and Ice
PostPosted: Fri Nov 16, 2012 1:53 pm 
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Hi folks,

I've been having a bit of a play with different colour choices for hydrogen emission nebulae. Here's a conventional rendition:

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      The Heart Nebula (IC 1805) - H-alpha + RGB

And here's a decidely unconventional rendition:

    Image

      The Heart Nebula (IC 1805) - H-alpha, synthesised H-beta + RGB

The lilac colour is the same colour I see in a hydrogen discharge tube which is, unlike astronomical nebulae, bright enough to trigger the eye's colour vision. Whether the discharge tube actually emits the correct proportions of hydrogen's Balmer Series (and nothing else) is a matter for debate on more specialist forums. :twisted:

Bob.

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PostPosted: Sun Nov 18, 2012 10:20 pm 
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Hmm, that's beautiful Bob!

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PostPosted: Mon Nov 19, 2012 12:59 am 
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Thanks, Thomas. 8)

Not sure which one you mean. The lilac colour will never catch on in the astrophotography community but for this particular subject I actually prefer it as the detail in the nebula seems clearer. As popo wrote elsewhere it's not a million miles away from leaving the H-alpha uncoloured which is a more acceptable alternative scheme in the community I think.

Bob.

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PostPosted: Mon Nov 19, 2012 10:25 pm 
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The red version is luring. But I never think of the universe as a warm and cozy place. So the lilac/cold version has its appeal...
Although a more blue tint would even be more appreciated :)
(P.S.: are there any differences in detail between the two versions?)

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PostPosted: Tue Nov 20, 2012 9:33 am 
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Hi Thomas,

No, the only difference between the two is the curve I used to colour the nebulosity layer but that does mean a slight change in mid-tone contrast as well as the overall brightening. I discovered yesterday that as the excitation in a hydrogen discharge tube increases the colour shifts more towards magenta. Whether that's down to a change in the physics or a physiological response of the eye/brain given how awkwardly the two major emission lines (H-alpha and H-beta) fall when mapped onto the response curves of the eye's colour receptors I can't say. But whatever the reason I don't think I can justify a blue version. :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: Tue Nov 20, 2012 10:34 am 
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Amazing image and even shows the face of an ET if you look closely.

In terms of the colour, will changing it have an effect on the "Redshift" theory of which direction and speed the object is moving? I can't claim to have much knowledge of the physics behind it but doesn't it base direction of travel and age of a celestial object based on colour? http://en.wikipedia.org/wiki/Redshift

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