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 MONO (de-bayered sensor) + 12Nm Ha filter exposure ~12 hours
ZWO ASI 071 MC Pro + LPS-P2 filter - exposure 19x360sec (2h 24min)
Total integration: 14 hrs 24 min