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Lying just 1.5 degrees east of the better known Lagoon Nebula in Sagittarius is this beautiful complex of nebulosity comprised of IC4684, IC1274, IC1275, IC4685, b303, NGC6559 and PK6-2.1.  This rich region of the sky combines red emission nebulae with regions of blue reflection nebulosity.  At the heart of IC4685, the dark nebula B303 meanders past a magnitude 7.3 star; one of several in NGC6559's open cluster whose visible and ultraviolet radiation powers this glowing complex.  At the left of this image, a tiny magnitude 16.0 planetary nebula marks the location of a red giant star that explosively cast off its outer layers.


Image info

Telescope:  Orion 80ED apochromatic refractor at f/7.5

Focus:  Prime focus

Filter:  Astronomik Hydrogen Alpha 13nm FWHM, Astronomik RGB.

Mount:  Vixen GPD with Skysensor2000

Camera:  Artemis 285 CCD camera

Guiding:  700mm refractor guidescope, SAC7 camera, autoguided with Guidedog software

Exposure:  Total 150 mins (30 x 300s) H-alpha, 33, 39, 93 mins R,G,B.

Date:  6th & 7th July 2006

Processing:  For all frames, offset and flat fielding, registering and stacking done in IRIS.  No dark frames.  RGB combination is first done in IRIS, and star colours are calibrated with a G2V star.  LRGB compositing, curve stretching,  Levels, Smart Sharpen in Photoshop CS2. 

LRGB compositing is through the process of "Luminance Corrected LRGB" as described by Steve Cannistra.  The R component of the RGB is first mixed with H-alpha in Photoshop and then recombined into a new RGB.  The Luminance layer was H-alpha mixed with desaturated RGB and with a correction layer whose opacity is reduced in subsequent iterations.  Pls see the link above for details.





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