Hydrogen in a bubble of Oxygen - The Crescent Nebula
© 2015 Eric Marlatt
This image is another attempt at narrowband imaging with a hydrogen-alpha filter and oxygen-III filter. Narrowband filters out much of the light pollution and allows for imaging when the moon is up, the individual frames to complete this image were taken with the moon 75% to 100% throughout the last month. This was shot through an Astro-Tech 8" RC with a QSI683 camera with Astrodon 5nm filters, pre and post processing done solely in Pixinsight.
The following was retrieved from Wikipedia, the free encyclopedia, at en.wikipedia.org/wiki/Crescent_Nebula on November 19, 2015.
"The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by Friedrich Wilhelm Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.
It is a rather faint object located about 2 degrees SW of Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or a Euro sign shape which makes some to call it the "Euro sign nebula".
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