For Northern Hemisphere observers, the Winter Triangle serves to identify an area of the Milky Way rich in deep-sky objects.
Sky & Telescope illustration, image courtesy Akira Fujii.
Much of the Milky Way is spangled with bright naked-eye stars, but not all of it. Southward from the feet of Gemini through Monoceros and northern Puppis, the Milky Way displays no star as bright as 3rd magnitude. Distracting the eye to the west of this region is Sirius in Canis Major. To the east is Procyon in Canis Minor. But don't be fooled; the "empty" sky between them is rich territory for deep-sky hunters with small scopes.
M50. Here's a cluster you probably don't know about, but it's easy to locate. Draw a line from Sirius in Canis Major through the Big Dog's nose, Theta (θ) Canis Majoris, and continue onward for nearly the same distance (about 4°). M50 is a faint smudge in a good finderscope, and a 60-mm telescope shows a group of about 20 stars. Through a 90-mm, the cluster's ¼° core reminds me of a housefly facing northeast. One wing goes off toward the south and the other to the west. Stars on the northeast side of the cluster form the head and mandibles. M50's brightest star lies in the southern wing; it looks reddish orange through telescopes larger than 4 inches.
Nearly 13° to the east-northeast of Sirius lies the open cluster M47. Visible in a good finder under suburban skies, M47 is notable for the two Struve double stars.
Draw a line from Mirzam, Beta (β) Canis Majoris, through Sirius and continue east for a little more than twice that distance, and you'll land just north of M47. Dark skies reveal a very faint fuzzy patch to the unaided eye. A good finder will pick it up under suburban skies. M47 is a beautiful cluster through any telescope. In a 70-mm, 25 bright to faint stars can be seen in a very loose, irregular group about ½° across. In a 4-inch, M47 shows about 50 mixed bright and faint stars weakly concentrated toward the center.
An arc of three fairly bright stars lies just north of center. The southernmost of the three is the double star Struve 1121 (S1121), a nearly matched pair of 8th-magnitude stars separated by 7.4". They can be cleanly split at 75x. M47's brightest star, near the western edge, is also double; Struve 1120 has 5.7- and 9.6-magnitude suns separated by 19". The brightest star north of S1120 is orange.