Natural color composition from the emission of ionized elements, R=80%Hydrogen+20%Sulfur, G=100%Oxygen and B=85%Oxygen+15%Hydrogen to compensate otherwise missing H-beta emission. This composition is very close to a visual spectrum.



The Cave Nebula, Sh2-155 or Caldwell 9 is a very diffuse 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.



Image is shot with a QHY8 and the Tokina AT 300mm f2.8 lens at full aperture.

Original versions from October 2008, with technical details:

http://astroanarchy.blogspot.com/2008/10/sh2-155-s-ii-channel-added.html

http://astroanarchy.blogspot.com/2008/10/sh2-155-cave-nebula.html