Celestial hemisphere:  Northern  ·  Constellation: Cygnus (Cyg)  ·  Contains:  Crescent Nebula  ·  HD192003  ·  HD192020  ·  HD192041  ·  HD192078  ·  HD192102  ·  HD192123  ·  HD192163  ·  HD192182  ·  HD192303  ·  HD192361  ·  HD192422  ·  HD192443  ·  HD192444  ·  HD192537  ·  HD192766  ·  HD192934  ·  HD228003  ·  HD228067  ·  HD228099  ·  HD228139  ·  HD228152  ·  HD228153  ·  HD228163  ·  HD228185  ·  HD228186  ·  HD228198  ·  HD228205  ·  HD228243  ·  HD228259  ·  And 53 more.
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Caldwell 27 - The Crescent Nebula, Monty Chandler
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Caldwell 27 - The Crescent Nebula, Monty Chandler
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I present to you the Crescent Nebula (NGC 6888, Caldwell 27, Sharpless 105).  My image contains 86 three minute subs taken the evening of Sept 2nd 2021 from my driveway in the hills of North Carolina.  Gear includes a SW Esprit 120ED telescope with the ASI071MC pro camera riding the SW EQ6r Pro gem mount.  Image acquisition via APT with guiding by PHD2.  Manually processed in Pixinsight. Jpeg creation done in Adobe Bridge.

Interestingly this nebula was formed violently by the fast stellar wind from the Wolf-Rayet star (WR 136) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.  WR 136 created this web of luminous material during the late stages of its life. As a bloated, red supergiant, WR 136 puffed away some of its bulk, which then settled around it in a vast, roughly spherical cloud. When the star evolved from a supergiant to a Wolf-Rayet star, it developed an even fiercer stellar wind and began expelling mass at a furious rate. The stellar wind collided with the material around the star and swept it up into a thin shell.

This stellar demolition zone lies within our own galaxy, about 4,700 light-years from Earth in the constellation Cygnus, the Swan. For best viewing, observe Caldwell 27 with a moderate to large telescope equipped with a light-pollution filter during the late summer from the Northern Hemisphere (or during the winter in the Southern Hemisphere). Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or a Euro sign shape which causes some to call it the "Euro sign nebula" (which I don't see). 

With a magnitude of 8.8, the Crescent Nebula is not visible to the naked eye — but if it were, it would appear in the sky as an ellipse one-quarter the size of the full moon.   C27 is a rather faint object located about 2 degrees SW of Sadr.    While it's commonly called the Crescent Nebula, Caldwell 27 looks more like a prehistoric dinosaur egg floating in space to me.  The fact that we can photograph it from our yard on earth amazes me.

In the future, the nebula’s shell may become compressed and begin glowing again, this time as a powerful blast wave moves outward from the Wolf-Rayet star when it completely destroys itself in a supernova explosion.  Something for future generations to photograph.

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Caldwell 27 - The Crescent Nebula, Monty Chandler