NGC 7635, a.k.a. the "Bubble Nebula", is an emission nebula in the constellation Cassiopeia. It lies close to the open cluster Messier 52. The "bubble" is created by the stellar wind from a massive hot, young central star.

Technical info:
TS 80mm f6 APO triplet refractor - Canon 40D + IDAS LPS2 (light pollution) filter - exposure 33x240sec (2h 12min)