The hot stars of the cluster [BDS2003] 66 appear embedded as pearls in a celestial oyster, the HII region Sh 2-211, in this unusually three-dimensional image created using the IPHAS data set, using the process described here. Sh 2-211 is believed to be ionised by at least three hot stars with the classes O9 Ib, O9 V and B0 V, and may share the same molecular cloud as Sh 2-212. Both nebulae are believed to lie well beyond the Perseus arm in what may be an Outer arm of the Milky Way.
This image is so interesting that I've included both a black and white hydrogen-alpha version and a false colour version that adds in the IPHAS Sloan r and Sloan i data as well. The hydrogen-alpha-only version reveals faint details obscured in the colour image.
