The Crescent Nebula (aka NGC 6888, Sharpless 105, Caldwell 27,) is an emission nebula about 5000 light-years away. The central star, the star of this whole show, is WR 136, and has an interesting history. It was born with 30 times our Sun’s mass, but then shed much of that mass into solar winds, becoming a red supergiant about 250,000 to 400,000 years ago. Once most of its’ hydrogen was consumed, it start burning helium, becoming an incredibly luminous blue supergiant Wolf-Rayet star. This burn is so intense that the star continues to shed its’ mass at high speeds, plowing into the previously ejected and slower moving material—this produces the ripples or fingers of matter, which are known as Rayleigh-Taylor instabilities. The intense UV light from the star causes all that gas to fluoresce. As it burns out the helium, the star will switch to burning lithium, and heavier and heavier elements up to iron, which cannot sustain a burn, so the ultimate result will be a powerful supernova.

The extremely dark blot in the center of the nebula is presumably a Bok Globule, which is a cold mass of dust and gas that is extremely opaque to light, blocking light from behind it. I have not found an official source saying so, it appears it is not a popular topic amongst the astronomical cognoscenti, and indeed very few remarks on it—if anyone has any info I would be very interested. 

This image was started using a LeNhance narrowband filter and for the last three nights continued with my new LeXtreme narrowband filter for the last 4 nights—both used to cope with my horrible Bortle 8 skies. Thanks to many of you out there who encouraged me to try the LeXtreme--both in your words and with the inspiration of your photos. As you promised, it is a substantial improvement over the LeNhance for NB targets like this.

I show two versions, personally I prefer the starless version, as the stars are distracting to the nebulosity--and to me make the whole image seem too grainy. Interested to hear what you all think...