Sh2-155 (also referred to as Caldwell 9, Sharpless 155 or S155 ) 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 . Sh2-155 is an ionised H II region with ongoing star formation activity, at an estimated distance of 2400 light years from Earth.
Photo taken by Team Aro in South Portugal in L,R,G,B. Total time 8h45, from 19/08 to 01/10/21

Autore: Team Aro (sito)