mage is in HST-palette, (HST=Hubble Space Telescope)

from the emission of ionized elements, R=Sulfur, G=Hydrogen and B=Oxygen.

Star colors are mixed from the NB channels, Red=H-a, G=O-III and B= 85%O-III + 15%H-a.



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