NGC 6888 or the Crescent Nebula (a.k.a. Caldwell 27 or Sh2-105) is an emission nebula located in Cygnus approximately 5,000 light-years away. Its formation is the result from stellar wind from Wolf-Rayet Star, WR136 (HD192163), colliding with slower-moving earlier ejected particles from the star when it became a red giant. The turbulent swirling ionized gas is quite impressive and measures approximately 25 light-years across. The red color is due to the high concentration of hydrogen gas while the blue-green is indicative of oxygen gas.
This object is probably one of the top ten most imaged objects and I have imaged this three other times myself. However, they were captured with different equipment. This is my most detailed version yet which makes sense since it was with my largest focal length scope. I am very happy with the result and am once again surprised at how much Ha and OIII came through using the IDAS NBZ filter. I love the blue-green outer nebulosity and if you look closely you can see it is dispersed throughout the object. Also interesting is the dark globule known as "The Bullet" in the center near the bright star HD192163. When I first imaged this years ago I thought it was a piece of dirt on the sensor.
After imaging this I broke down this rig as I was having intermittent technical difficulties between the ASIAIR Pro and EAF. The ASIAIR would not read the EAF when starting up. Thinking it was the cables I went through four sets before determining that was not it. I contacted ZWO and have to say they were quite responsive in particular, TJ Connelly. Long and short, I ended up sending both items to New Jersey and they had to replace the EAF motor - very happy with the service.
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