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Tom Arrington | all galleries >> Tom's Astrophotos >> 2009 > Crescent Nebula - NGC6888
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Crescent Nebula - NGC6888

A dim nebula nestled in the constellation Cygnus amongst the Milky Way. Near the star Sadr, the middle star in the swan's body. "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 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward." Wikipedia

The bright star in the center of the nebula is the Wolf-Rayet star. It is predicted that this star will end its life with a super nova. The star and nebula are about 5,000 light years from the earth.

This is the result of a "lost" opportunity weekend. I had planned on getting at least 4 hours of exposures for this object. Both Friday and Saturday were to be clear, moonless nights with very good conditions. Friday was a complete bust. I was fighting software issues with my mount and wasted at least one hour with that. By the time I was ready, unexpected clouds had rolled in. Home at 3:30am with nothing to show for it. Saturday was partially cloudy all day in spite of a clean Clear Sky Clock. It did clear up after dark, but I didn't get stared until 2 am (a longer nap than planned). The sky was perfect, all of my equipment seemed to be working flawlessly. The first exposure looked good. I captured the first hour and everything looked good. Slew to Sadr to refocus and only a minor adjustment was needed. Back to the Crescent, change the camera battery and run the next hour and beat the morning light. DSLR Focus gave me a warning, which in my sleep depraved condition I ignored. Big mistake! After reestablishing the connection of the camera and software, the save mode had changed to the camera not the computer. Well the CF card was not plugged in all the way. SO - I took an hour of exposures under a nearly perfect sky and didn't save any of them!

Bottom line - 66 minutes of exposure time and it needs more, but I won't be able to get out again soon, so here it is until I get some additional time and update it.

Taken August 23, 2009 west of Columbia, MO
Camera: Canon Rebel XT modified by Hap Griffin
Telescope: William Optics FLT 110 Lite with a WO Reducer Flattener III system at f5.6
Mount Celestron CGE guided with PHD Guide via a Meade DSI Pro
Exposures: 11 x 360 seconds ISO800
Processing: Deep Sky Stakcer with Darks and Flats, PixInsight LE, Photoshop CS3

other sizes: small medium large original auto
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