The Bubble Nebula, aka NGC 7635, formed from a bright star inside a cloud of (mostly) hydrogen. The star's intense radiation pushes material outward and concentrates it, and also causes it to glow. This is a synthetic-color image mostly from the hydrogen-alpha emission line, but with some oxygen emission added in. The field of view here is about 3/4 of a degree, or a little bigger than the size of the full Moon.

H-alpha 27x180" at 110 gain
OIII 18x300" at 270 gain