This image is the composite of 18, 6-minute frames taken from the backyard observatory’s 130mm astrograph fitted with a quadband filter. The Wikipedia entry for NGC 6888 has even more beautiful images of the Crescent.
Five thousand light years away, a massive star rapidly expanded to become a Red Giant, cast off its outer hydrogen shell, and began a new life as a Wolf-Rayet star (WR 136) now deriving its energy by fusing helium rather than by fusing hydrogen. That gas shell was cast off an estimated 250,000 years ago. It is falling back toward the massive WR star, but the star itself continues to eject material with much greater energy than that of the castoff gaseous shell has. So, the effect is two colliding gas shells moving in opposite directions. We see it as the Crescent Nebula, NGC 6888.