This vast emission nebula in Monoceros spans roughly 130 light-years and lies about 5,200 light-years away. The central open cluster NGC 2244 formed from this very gas cloud around 4 million years ago, and the intense stellar winds and radiation from its hot O-type stars have since carved a wide hole in the nebula’s centre — giving it the characteristic rose shape. The Duo-Band filter is essential to cut through Edinburgh’s light pollution and reveal the hydrogen-alpha structure.