Sh2-155 - The cave nebula

This one took me a while

This narrowband photo probably holds the record for myself on the amounts of nights spent trying to image the same target. Having spent over 12 nights on this object I kind of grew frustrated with the bad weather. Lots of these nights I setup my telescope only to find the sky to be completely foggy after 1-2 hours (fall weather I guess). This was especially true for the O-III (oxygen) data which got quite the bloated stars due to imaging through some thick fog.

Because of this, a blueish halo is visible around the stars in the image, I was not able to correct for it in post-processing. To be honest I am not really happy with the results, but still decided to publish it just to show that not every photo turns out as nice as I wish it to.

Now on to some information about this nebula

The Cave Nebula (also designated “Sh2-155”) is an object that is not photographed that often by amateur astronomers. It is a diffuse emission nebula located 2400 light years from earth. The red parts in the nebula show the abundant Hydrogen through the Hydrogen-alpha line at 656.28nm (which we humans perceive as red).

Whereas the blue parts show the (foggy) Oxygen data and greenish parts (only visible as orange in the bright red parts) show the Sulfur inside the nebula.

Being an active star forming region, it is theorized that the radiation from the hot O-type star HD217086 is compressing the gas in this nebula. The compression of the gas then triggers the birth of new stars and star systems

Further studies from the Chandra X-Ray observatory and Spitzer Space Telescope revealed a progression of stellar ages in front the cloud, further confirming this theory.