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Sunday, May 23, 2010

M16, the "eagle nebula" in HST-palette

M16, HST-palette, RGB-stars

Cropped detail from image n HST-palette and with a broad band RGB-stars.

I don't usually like to mix images, made with totally different technique. How ever, it's very common among many astro photographers to mix broad band stars to a narrow band image. 
The reason is, there is no real stars colors in NB imaging and generally stars are heavily suppressed due the very narrow band width used in filters. 
Some times it's a good thing to have little suppressed stars to be able to show the Nebulous better. 

imaged with a Northern Galactic members remote telescope in Australia,

16" RCOS ja Apogee U9000 camera. 
LRGB combo.
H-alpha 5x1200s, O-III 2x1200s, S-II 2x1200s . Dark and Flat calibrated.
Raw data is shared with Petri Kehusmaa and J-P Metsavainio

Processing workflow:
Image acquisition, MaxiDL
Stacked and calibrated in CCDStack.
Deconvolution with a CCDSharp, 30 iterations.

Levels, curves and color combine in PS CS3.
Narrow band lines are mixed to a HST-palette (Used generally with Hubble Space Telescope)
Red=S-II, Green=H-alpha and Blue=O-III

EDIT. 25.05. 2010
All the pure HST-palette NB images are now updated. Stars are redone by using information from all the NB-channels. By this way, Stars are somehow large but overall feel is more natural, than by using stars from the H-alpha channel alone, as I have done before.
My "Tone mapping" procedure is used to make this image, a tutorial for it can be found here:
Since stars doesn't have any relevant color information in HST-palette images, due the broad band nature of Star emission, I have developed a powerful method, Tone Mapping, to process NB images.
Now on I'll add a star information from all the channels, not just from H-a.
I will rewrite the "Tome Mapping" document in near future.

All NB Channels

Channels are "Tonemapped", all the high S/N components = Stars, are removed to build a well balanced color Map.

A Starless "Color Map", build from channels above.

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