In the Jan/Feb 2006 Australian Sky & Telescope David Frew profiled Canis Major. He notes that the central star (Tau CMa) is a triple. I hadn't noticed it before as there are a considerable number of cluster stars. This is one of my favourite cluster, one of which many amateurs are unaware. Very close by is the Herschell double with the green and gold contrasting stars. One of the best in the sky, other than Albiro