A Cluster of Clusters

M46. This cluster lies just 1.3° east-southeast of M47 and offers a study in contrasts with it. M46 appears much smoother and finer grained than its coarse, bright-starred neighbor. Look for a glowing swarm of hundreds of faint stars, many just on the edge of visibility through a 70-mm scope. In a 4-inch M46 appears round and extremely rich, with many faint to very faint stars densely packed over an unresolved background.

NGC 2423. There's a third cluster here too. Just 40' north of M47 a 60-mm telescope will pick out a small, faint patch of light. Much subtler than its splashy neighbors, NGC 2423 looks about half their size. Through a 4-inch it shows about 20 dim stars against an unresolved haze.

Together M47, M46, and NGC 2423 make up one of the prettiest fields in the sky for small rich-field scopes. At 25x or less all three will fit in the same field of view. Because they appear strikingly different, the total effect is breathtaking. It is even more fascinating if we keep in mind the trio's relative placement in space and time. M47 is the closest and youngest at about 1,400 light-years and age 200 million years, while NGC 2423 is approximately twice as old and distant. M46 is about the same age as M47 but more than three times farther away, at around 5,000 light-years.

M48. This cluster is 12° farther northeast. It makes a not-quite-equilateral triangle with the 4th-magnitude stars C Hydrae (a wide triple in binoculars or a finderscope) and Zeta (ζ) Monocerotis. A 60-mm shows a big, poorly defined group 40' wide made of about 30 stars 8th magnitude and fainter. The brighter stars run north-south across the center. A 4-inch scope shows 50 stars, many arranged in pairs and chains.