NGC6888 AKA Crescent nebula - An interesting cloud of gas and dust is located in the constellation Cygnus close to Sadr, the central star in the northern cross.
The star responsible for the nebula’s shape and glow is the Wolf-Rayet star WR 136 (HD 192163). The nebula is formed by the star’s fast, powerful stellar wind that collides with the slower wind ejected by the star about 250,000 years ago, when WR 136 expanded to become a red giant. The collision has produced a dense shell, which continues to expand at a speed of 80 km/s, and two shock waves. One shock wave is moving outward from the shell and producing the green filamentary structure visible in images, while the other is moving inward to create a bubble of gas that is heated to X-ray emitting temperatures. The hot gas ejected by the star moves at speeds of 2,000 to 3,000 km/s and the star sheds about a solar mass of material every 10,000 years.
Reference -
constellation-guide.com/crescent-nebula/About my experience capturing this picture -
I acquired the data for this image at Los Angeles backyard, Bortle 9 skies.
Learning - Stars don't lieThe biggest challenge during project was guiding. It was during my first few days of imaging with long FL refractors. The guiding looked great on PHD2 logs, but the stars were elongated. I narrowed it down to focuser sag and balancing. Couldn't do much, but I am not throwing away these subs before I add more data.
I haven't been imaging. So I am picking up new techniques for processing. Happy with the current results. Looking forward to add more data and learn new processing techniques.
Happy to hear your feedback and comments.
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