All but two of the fifteen Bochum open clusters reside in the southern hemisphere and one of the two (Bochum 2) lies on the cusp at a declination of +00 23 00… almost a southie! The Bochum clusters can be found along our summer Milky Way in Gemini, Monoceros, and Puppis, with a couple in our rich winter Milky Way constellations Scorpius and Sagittarius.

They are a wonderful collection of open clusters to observe, one of which – delicate Bochum 10 – is surely one of the loveliest open clusters to see in the eyepiece, lying as it does just off the southern edge of the huge and gorgeous Wolf-Rayet Bubble WR 23 which itself lies embedded in Eta Carinae Nebula’s billowing three-dimensional cloudscape! What more could you ask for in an open cluster observation?

The 15 Bochum open clusters were discovered during a UBV Hβ photometry survey of southern open star clusters carried out by A. F. J. Moffat & N. Vogt in 1975. They carried out the observations with the La Silla Bochum 0.61-metre telescope, hence the designation.

The Bochum telescope at La Silla. Credit: ESO/C. Sterken

The Bochum 0.61-metre telescope, installed by the German Research Foundation and Ruhr University Bochum on La Silla in 1968, has the honour of being the ESO’s first national telescope (a telescope which is the property of one of the member states and, as compensation for ESO services, ESO obtains a fraction of the observing time). The telescope has since been decommissioned… but it lives on in these 15 beautiful clusters.