The Cave Nebula, Sharpless-155 or Caldwell 9, is a star-forming hydrogen region in the constellation Cepheus, about 70 light-years in diameter and 2400 light-years away.

I collected oxygen-III as well as hydrogen-alpha data but the OIII was pretty awful, led to severe color gradients that I simply didn't feel up to banging on. So this is just Ha, 6.7 hours of exposure time over six nights in my driveway.