The California Nebula is a diffuse nebula in Perseus. In shape it resembles the US state of California. It is illuminated by the hot star Xi Persei, seen above the nebula in the above photo, just left of centre.
This image was taken on the night of 19 November 2013 through a Canon 200mm f2.8 camera lens and a hydrogen alpha filter with an Atik 460EX mono CCD camera. It consists of 17 x 900s sub exposures.