The Cave Nebula

I shot this target 29.11. but I'm publishing it now since this one was very hard to process due to its dimness.

Cave Nebula, Sharpless 155 (Sh2-155)

In constellation Cepheus

Image in mapped colors from the light emitted by ionized elements. 

Red=Sulfur, Green=Hydrogen and Blue=Oxygen.

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.

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.

Orientation in a wide filed image

Area of interest is marked as a white rectangle. More info about this image HERE.

An apparent size of the full Moon is marked at the lower right corner for a scale.

Click for a large image.

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 seen above.

Ps.

A single 20 min. H-alpha frame

Calibrated with Bias corrected flat and Dark masters in CCDStack

1200 seconds of H-aplha light with 12" SCT @ f5 and QHY9 astrocamera.

Image is scaled down 50% from original.