Another night of semi clear sky, but a host of problems with guiding. I finally resolved my issues around 00:45 and finished the night at 03:30. This is the first time I attempted NGC6888, I was going to try and image more but as usual in about 30 min the sky around here would be too bright, so I called it a night and went to sleep. I am not really happy with this image but for now it's the best I can do. I am thinking maybe processing in PixInsight vs SIRIL. I used drizzle hoping to bring out a little more detail. I am a little tired since I only got in about 3 hours of sleep, I am going to attempt better processing but for now I am sort of happy with what I have done so far.The
Crescent Nebula (also known as
NGC 6888,
Caldwell 27,
Sharpless 105) is an
emission nebula in the constellation
Cygnus, about 5000
light-years away from
Earth. It was discovered by
William Herschel in 1792. It is formed by the fast
stellar wind from the
Wolf-Rayet starWR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a
red giant around 250,000 to 400,000[
citation needed] 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.It is a rather faint object located about 2 degrees SW of
Sadr. For most telescopes it requires a
UHC or OIII filter to see. 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 makes some to call it the "Euro sign nebula".
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