Crescent Nebula in HOS (David McClain)

Celestial hemisphere: Northern · Constellation: Cygnus (Cyg) · Contains: Crescent nebula · NGC 6888 · The star 34Cyg

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Crescent Nebula in HOS

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Crescent Nebula in HOS

Raw frames courtesy of Deep Sky West Remote Observatory in New Mexico, USA. (deepskywest.com) Data obtained with FSQ 106EDXiii / QSI683wsg / Lodestar / Paramount MyT.

25 hrs total integration (18x1800s H, 17x1800s O, 15x1800s S). The palette is the CFH palette where HOS is mapped to RGB. Optimally weighted Luminance was derived from the three color channels and applied. Because these narrowband filters already diminish the overwhelming field stars, no star erosion was applied to this image. The color saturation in the wings of the star images was reduced, to remove much of the magenta halos around stars.

Processing in PixInsight.

This image is really good at separating the various elements. The deep red arises from H-II emission. The yellow/green arises from the blend of H-alpha with O-III. There isn't very much S-II in this image, which would show as blue. You can just barely detect its presence in the magenta faint wisps of clouds above the Crescent Nebula.

The magenta hue on some stars arises because over the broadband region encompassing both H-II and S-II, roughly equal amounts of energy makes its way through the two filters. Both of these filters are deep red, very narrow band (3-5 nm) and separated by only 16 nm, down around 650 nm wavelength. But by making S-II into an artificial blue, we end up with magenta stars.

The main takeaway with this image should be the strong presence of ioniozed Oxygen in the Crescent Nebula. That doesn't come across nearly as well in a standard RGB image.

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	Image of the day	Top pick	Top pick nominations	Total submitted
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	Image of the day	Top pick	Top pick nominations	Total submitted
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The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

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Status	Basic success
Started	...
Astrometry.net job	1166383
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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Crescent Nebula in HOS

Crescent Nebula in HOS

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Crescent Nebula in HOS

Crescent Nebula in HOS

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