Crescent Moon is an easy target for any stargazer. However not many know that we have another crescent in the sky. This one is well hidden in constellation Cygnus and cannot be viewed with naked eye – the Crescent Nebula (NGC6888) shines faintly somewhere there and can be spotted with medium sized telescopes using filters. Nebula is placed about 4000 light years away and is formed by stellar wind from Wolf-Rayet star colliding with slower moving wind ejected by the star when it become a red giant star a few hundreds of thousands years ago. The result of this collision is a sheel and two shock waves. The red giant center star will some day (in about one million years) explode as supernova, and then whole this space region will be changed.
Picture at the top is enlarged crop of the full frame (below). It has been shot through Hα Baader filter with total exposure time of 3 hours and single exposition of 10 minutes.
Clear skies!
