NGC 6888 -- Crescent Nebula in Cygnus
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A Wolf-Rayet Nebula
At the center of the Crescent Nebula is the Wolf Rayet Star, WR-136.  Wolf Rayets are
luminous-hot dying stars that shed massive amounts of energy and material into space.  
In the case of WR-136 the material is ejected at speeds of up to 3,000 kilometers per
second.  When the new material hits previously ejected material it lights up creating a
bubble-like emission nebula.  Currently the Crescent Nebula is 25 by 16 light years across.

The Crescent Nebula shows its true bubble-like shape in professional telescopes, but
through small to medium-sized amateur telescopes one can only make out the brighter
sections. The crescent shape of these brighter sections of the nebula provides its common
name.  WR-136 shines at the center of the nebula at magnitude 7.7 and is easily identified
since the crescent wraps around it.

I only had a couple hours between sunset and the rise of a bright gibbous moon.  But the
sky was clear and transparent, and it would have been a waste not to spend the short time
that I had at the telescope. The Crescent Nebula filled the time nicely.