Here is Crescent Nebula (NGC6888) with OIII (Oxygen III) narrowband layer (that is creating the blue halo around this nebula).

This is a cosmic bubble about 25 light-years across, blown by winds from its central, bright & massive star. The central star is classified as a Wolf-Rayet star i.e. the star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun’s mass every 10,000 years. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

It’s named Crescent due to it’s shape. Now, some call it Euro Nebula as its shape matches the currency sign.

This was shot over 19 hours (15 Luminance of 30 min each, 7 images of RGB colors of 15 min each & 19 OIII images of 20 minutes each).