Description (wikipedia)

Sh2-155 (also designated Caldwell 9, Sharpless 155 or S155, or LBN529) is a diffuse nebula in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity. It is widely known as the Cave Nebula, though that name was applied earlier to Ced 201, a different nebula in Cepheus. Sh2-155 is an ionized H II region with ongoing star formation activity, at an estimated distance of 725 parsecs (2400 light-years) from Earth.

Sh2-155 was first noted as a galactic emission nebula in 1959 in the extended second edition of the Sharpless catalogue, being a part of the much larger Cep OB3 Association. Although Sh2-155 is relatively faint for amateur observation, some of its structure may be seen visually through a moderately sized telescope under dark skies.

Sh2-155 lies at the edge of the Cepheus B cloud (part of the Cepheus molecular cloud), and is ionized by young stars from the Cep OB3 association. It has been suggested that radiation from the hot O-type star HD 217086 is compressing the region, triggering the formation of a new generation of stars. A study of the region's young stellar objects by the Chandra X-ray Observatory and Spitzer Space Telescope shows a progression of stellar ages in front of the cloud, supporting the hypothesis of triggered star-formation.

Personal Note

I tried some new narrowband processing workflows on this image, including Fornaxx and the flow presented int he recent Pixinisght playlist on YouTube.Fornaxx gave an image that was just too red for my taste, while the other method yielded some nice results. I also did a more traditional workflow using SCNR to remove the green.


Process workflow
Chrominance: DBE, Deconvolution, Denoising, background neutralization, color polarization using pixelmath, GHS for stretching, StarXt, clonestamp to remove large streaks from a star just outside of the FoV, Curves to enhance color and contrast.
Luminance: extracted L* component from SHO, mixed 1/3 high dynamic range, 1/3 sharpened and 1/3 original to create master Lum.

Please let me know your feedback and your suggestions on how to improve further. Thank you!