The Cave Nebula, Sh2-155 or Caldwell 9, is a dim and very diffuse bright nebula within a larger nebula complex containing emission, reflection, and dark nebulosity. It is located in the constellation Cepheus. The reflection, wide band, component can't be seen in my image, since this is a narrowband one.
Distance is about 2400 light years.

Technical details:

Processing work flow:
Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Levels, curves and color combine in PS CS3.

Optics, Meade LX200 GPS 12" @ f5
Camera, QHY9
Guiding, SXV-AO, an active optics unit, and Lodestar guide camera 8Hz
Image Scale, ~0,8 arc-seconds/pixel
15x 1200s exposures for the H-alpha, emission of ionized Hydrogen = 5h
Narrowband cahnnels for ionized Oxygen and Sulfur are taken from an older wide field image.