M35 — My Favorite Cluster

M35 is my personal favorite open cluster. Located about 2½° northwest of Eta (&eta) Geminorum, it is an impressive frame of bright stars with a softly flaming background of fainter ones, seemingly containing hundreds of members. Charles Messier, however, was not the first to call attention to M35. That honor appears to go to the Swiss astronomer Phillipe de Cheséaux, who in 1746 called it "a star cluster above the northern feet of Gemini."

Amateurs often test themselves by trying to view the cluster with the naked eye. This puts it in the same class as the galaxy M33 and the zodiacal light. Brian Skiff in Arizona concluded from a study of 434 stars in M35 that its total magnitude was 5.1, but the bright background glow of the Milky Way may be a handicap. Nevertheless, one clear morning in September 1984, Sky & Telescope's Dennis di Cicco chanced upon the cluster with his naked eye.

To me, M35 seems most lovely in a 6-inch at 40x — though I must admit that, through a 36-inch telescope and a wide-field eyepiece, this blaze of interwoven stars is an awe-inspiring sight. With a home-made wide-field eyepiece on my 10-inch reflector I could get all of M35 into a single field. The view was too beautiful to describe with mere words. Bright stars were scattered with cosmic recklessness across the field, and it was difficult to establish where the cluster's edges dissolved into the stellar background.

The Rosette Nebula in Monoceros (see "Observing Nebulae Season by Season") is an object with far better name recollection among today's amateurs than NGC 2244, the open cluster it surrounds, even though the latter was the only object mentioned in observing guides until recently. NGC 2244 was itself once a test for the naked eye. The brightest star here is 6th-magnitude 12 Monocerotis, but it's quite likely a foreground star and not an actual member of the cluster. Sky Catalogue 2000.0 lists NGC 2244 as having about a hundred stars and a total brightness equal to that of a 4.8-magnitude star. With an estimated age of 3 million years, the cluster is very young; in fact, the Rosette Nebula is the cloud of gas and dust that gave the cluster its birth.