The Bubble Nebula, NGC7635 and Sh2-162, is an emission nebula in Cassiopeia. It’s near the cluster M52 (I’m working on a wide-field image now that has both the Bubble and M52). The bubble itself (about 10 light years across) is formed and pushed out by a massive star in the middle of the bubble — its stellar wind irradiating the gas and causing it to glow.
The image is a combination of 30 360s exposures with a Canon T4i (modified to allow Ha light) and Edge 11″ SCT at f/10. Taken from a dark site in southeastern Utah.
Resolution ........ 0.317 arcsec/pix Rotation .......... 80.736 deg Focal ............. 2926.53 mm Pixel size ........ 4.50 um Field of view ..... 27' 15.0" x 17' 32.0" Image center ...... RA: 23 20 32.383 Dec: +61 11 12.85