The Messier objects that are at their highest in late-winter evenings are less diverse than the early-winter objects; all of them are open clusters. However, it is a fine and varied lot of open clusters. Here are the objects from RA 6 to RA 9 excluding M35, which was covered in the preceding section.
For a key to this table, see
Key to the Tables.
In addition, many of the early-winter objects are well north of the Celestial Equator, and so remain visible throughout the winter to observers in the North Temperate Zone. Not so for the late-winter objects, most of which lie south of the Celestial Equator, and so are only well placed for a short time for observers in the North Temperate Zone.
The disparity between the early-winter and late-winter objects is no accident; it is due to the fact that the Milky Way slants south-east through this part of the sky, passing through Auriga, then between Gemini and Orion, and disappearing for northern observers in the constellation of Puppis, southeast of Canis Major. Open clusters and nebulae tend to hug the plane of the Milky Way, so the farther east you go in this section of the sky, the farther south the open clusters and nebulae are found.
In striking contrast to the early winter Messier objects, all of the late winter objects except for M41 are far from bright stars, making them difficult to locate under urban skies. I usually quote the limiting magnitude for my urban sites at mag 4.6, but that assumes the use of averted vision, knowing exactly where to look. Only stars mag 3.0 and brighter really catch my eye; stars between mag 3.0 and 3.5 are not hard to see, but require some looking, and anything fainter than mag 3.5 requires real effort. This part of the sky is dominated by the constellations Monoceros and Cancer, whose brightest stars are mag 3.8 and 3.9 respectively. That leaves an enormous expanse of sky which at first glance appears entirely devoid of stars. The “beacons” of the area are Zeta and Chi Hydrae in the head of Hydra, at mag 3.1 and 3.4 respectively; it is worth spending some becoming familiar with them. Take a look at Hydra’s head in binoculars; it is a wonderful asterism.
Under decent suburban skies, enough extra stars are visible to make navigating this part of the sky a pleasant adventure instead of a heroic exploit.
If you are planning to observe all of the Messier objects and live in the North Temperate Zone, you would be well advised to observe M81 and M82 at this time of year. These objects are at their highest in the early spring, and are described in that section of this guide. But being the most northerly of all the Messier objects, M81 and M82 are high above the horizon long before and after that time for observers in the North Temperate Zone. If you save all the galaxies for spring, you are likely to be overwhelmed by them.
M41 is very big and very bright; in fact, it is readily visible to the naked eye under dark skies if you live far enough south for it to rise high above the horizon, and it is fairly easy in my 7×35 binoculars even from my city home at latitude 42N. It shows very well in my 70mm scope under urban, suburban and dark skies, but it improves little if at all in larger telescopes; it is not especially rich in faint stars. Because M41 is very big and somewhat vague, it needs a very large field of view to set it off well against the fairly rich background — preferably 1.5 degrees or more.
I can usually find M41 fairly easily by the point-and-hope method, aiming 1/3 of the way from Sirius to Epsilon CMa, the bright star at the right-hand foot of Canis Major. If that fails, the best bet is to star-hop from Sirius.
M41 contains three mag 7 stars, resolvable even in small binoculars. True to form, two of those stars are near the cluster’s center, one strikingly red, and the other appearing reddish yellow to my eye. I see about two dozen stars using my 70mm scope in the city at 20X, many at the edge of visibility, giving it a charming air of mystery which vanishes in bigger scopes and darker skies. Some 50 star are visible in my 178mm scope at 28X under suburban skies, spread out fairly evenly from mag 8 down to mag 11.
M50 is a modest but attractive cluster, fairly small and fairly bright, and it stands out surprisingly well against a very rich background, especially at higher powers. It contains five or six stars brighter than mag 9.5, but the majority of the stars are mag 11 or fainter. My 178mm scope resolves the fainter stars well, but in my 70mm scope they tend to merge into a nebulous background, which is fairly prominent in the suburbs and rather subtle from the city. M50 does best at high powers, 60X in my 70mm scope and 120X in my 178mm. M50 is fairly difficult to see in my 7×35 binoculars from the city or the suburbs.
The stars of M50 line up roughly in the shape of an equilateral triangle, with four stars forming a tiny horizontal Y in the center. The brightest star of the cluster, near the south tip of the triangle, shows strikingly red in my 178mm scope.
M50 is fairly easy to locate from Theta CMa at the top of the Big Dog’s head, but at mag 4.1, that star may be impossible to see from northern cities due to its low altitude above the horizon. Extend a line from Sirius through Theta and continue 80% farther; there lies M50. If you cannot see Theta, you must star-hop from Sirius.
M46 and M47
M46 and M47 are visible together in a 2-degree field, and they form a wonderful contrasting pair. The two clusters are almost identical in size, but there the similarity ends. M47 is extremely bright, quite prominent to the naked eye under dark skies. It is a fairly sparse cluster, dominated by a handful of very bright stars. M46 is several times fainter, very rich in faint stars, but with no bright stars whatsoever.
M47 contains 5 stars brighter than mag 7.5, all easily resolved in my 7×35 binoculars under urban skies, let alone in my 70m scope. Somewhat surprisingly, these stars do not stand out all that well, due to the proximity of several other similarly bright stars in the immediate vicinity. About twenty stars are visible in my 70mm scope under urban skies, enough to make the cluster seem convincing, although still rather sparse. Darker skies and/or larger apertures bring out another 20 somewhat fainter stars which help to flesh out the cluster. M47 shows well at 40X in both of my scopes, and this is also enough power to split the attractive double star Struve 1121 at the center of the cluster, with two almost equal blue-white components separated by 7″.
M46 is an extremely rich collection of faint stars, quite similar to M37, although the stars are little fainter and more scattered than those of M37. Under dark skies, the faint stars merge into a haze that stands out well in my 70mm scope and my 7×35 binoculars, and may even be visible to the naked eye, but this haze is too faint for me to see even in the suburbs, let alone the city. Under urban and suburban skies, I can detect the cluster only when I can resolve some of the stars, which is far beyond the capabilities of my 7×35 binoculars, and also difficult or impossible in my 70mm scope at low powers.
In my 70mm scope at 60X, only a handful of M46’s stars show from the city, most of those with averted vision. Things improve considerably in the suburbs, with 12 stars visible using direct vision and many more popping out intermittently with averted vision.
M46 is still a little difficult using my 178mm scope at low power in the city; I have scanned right over it at 40X without seeing it. But once I pinpointed the location, a large number of stars were evident, some visible with averted vision, some with direct vision, but none bright enough to catch my eye unless I looked carefully. The cluster improves greatly at 120X, where numerous faint stars almost fill the field of view.
M46 really comes into its own using my 178mm scope in the suburbs, where numerous stars are immediately obvious both at low and at high powers.
At higher powers in my 178mm scope, the planetary nebula NGC 2438 is faintly visible near the northern edge of the cluster. It is hard to pick up under brighter skies, but jumps out immediately with the aid of a narrow-band filter, which erases many of the cluster’s stars while leaving the planetary nebula unchanged. This nebula is believed to be an accidental superposition, unrelated to the cluster, and lying some distance behind it.
M46 and M47 are fairly easy to locate off Alpha Monocerotis, some 5 degrees to the north. However, this star is quite hard to see in the city, being only mag 3.9, and very far from any other visible star. If you cannot find alpha Mon, you are faced with a very long hop from Sirius.
M93 is a bright, highly condensed, and attractive cluster. Unfortunately for northern observers, it is fairly far south of the Celestial Equator, making it a little hard to see under heavy light pollution. Even so, it is visible at latitude 42N in my 7×35 binoculars as a small but well-defined patch of light, quite easy to see in the suburbs and fairly difficult in the city.
In my 70mm scope at 60X in the city, I see two bright mag 8 stars, an obvious mag 9 star, six faint stars, and another six or so with averted vision, all in a 15′ circle. The view is similar in the suburbs except there is also a hazy background shimmering with stars that appear fleetingly as I scan with averted vision.
In the 178mm scope, the cluster is framed best at around 60X but shows more detail at higher powers. Some two dozen fairly bright stars form the outline of a reverse P or ampersand (see upside-down in my Newtonian), and under suburban skies, I count another two dozen faint stars within a 20′ circle, although these fainter stars do not contribute much to the appearance of the cluster.
M93 is very easy to find off Xi Puppis (mag 3.3), which I can see fairly easily both in the suburbs and the city, despite its low altitude. Xi forms a fine pair with Rho Puppis (mag 2.7) 4 degrees to the east. If you cannot see Xi or Rho, you can always star-hop from brilliant delta CMa.
M48 is a large, bright, and interesting cluster which shows well in large and small scopes and resists light pollution well at medium to high magnifications.
Under dark skies, M48 is prominent in small binoculars and faintly visible to the naked eye. From the city and suburbs, it is vague and ill-defined in my 7×35 binoculars, which resolve only a few bright stars, not enough to add up to a cluster. The remaining stars form a haze with very modest surface brightness which is easily masked by skyglow.
M48 shows best at 40X – 60X in my 70mm scope, with the lower powers framing the cluster better and the higher powers showing more stars. I see about 15 stars in the city and about 25 in the suburbs. My 178mm scope shows 40 or 50 stars, much the same in the city and the suburbs. Again, 40X frames the cluster best, but higher powers resolve the cluster better, especially near the center.
The stars of M48 fall easily into patterns, but the patterns are fluid and elusive. Sometimes I see 3 or 4 bright stars near the north edge and a line of fainter stars oriented east-west near the center of the cluster, forked into a horizontal Y at the west end. Other times, I see all of the stars forming an equilateral triangle 30 minutes on a side, with that center line transforming into three spokes linking the center to the sides. Regardless, the cluster hangs together well despite its large size and the wide range of brightness of its stars.
M48 can be rather hard to locate. I like to start from the line of stars 1, 2, and c Hydrae, a lovely asterism in binoculars and small telescopes, and to the naked eye under dark skies. C Hydrae, at mag 3.9, should be visible to the naked eye under most skies; it is fairly easy to locate off the head of Hydra. If that fails, you will have to do the heroic 14-degree star-hop from Procyon.
M44 is one of the few deep-sky objects that unquestionably shows better in binoculars and small telescopes than in large telescopes. It also is hurt very little by light pollution, although light pollution makes it much harder to find. Under dark skies, M44 is readily visible to the naked eye as a fairly large patch of fuzzy light, and I also find it fairly easy under decent suburban skies, and visible with considerable effort from the city. However, it is in an extraordinarily blank part of the sky; no star within 15 degrees is truly prominent under heavy light pollution. Delta Cancri is very close, but at mag 3.9, it is barely easier to see than M44 itself. If you cannot see either, you are faced with a very long star-hop beta Cancri (mag 3.9) 12 degrees to the SW, or from Zeta and Xi Hydrae (mag 3.1 and 3.4) 13 degrees to the S, possibly via M67, or if all else fails, from dazzling Pollux 15 degrees to the NW.
M44 is enormous, as big as the Pleiades, and because of its rambling shape, it requires a very large field of view to frame it well, preferably at least three degrees. This object is a perfect match for my 70mm scope at 16X, which allows me to resolve at least 30 stars in the city. I can see more stars using the same scope in the suburbs, but they do little to improve the appearance of the cluster. Even my 7×35 binoculars resolve some dozen stars in the city and two dozen in the suburbs, yielding a very attractive view of the cluster.
Although the stars of M44 are quite sparse, they form into attractive geometric patterns, and the cluster contains numerous double and triple stars. Most of the brightest stars show strikingly red or yellow through my 178mm scope, reflecting the fact that this is a fairly old cluster. In my 178mm scope, the cluster looks best in the widest field the scope can deliver, 2.4 degrees at 28X using a wide-field eyepiece. Higher powers merely make the cluster look coarse and vulgar.
M67 is one of the oldest open clusters known, probably between 4 and 5 billion years old, about as old as our own solar system. Normally, open clusters are fairly short-lived in cosmic terms. In fact, most astronomers believe that all stars originated in clusters, but most of the stars that we see today are free-floating, and most of the clusters that we see are much younger than an average star like our own Sun.
The ephemeral character of open clusters is due to the fact that stars continually evaporate from the surface, or are torn off by the tidal force of the galactic disk. M67 survives because it is unusually rich and dense, so that gravity binds it more tightly than most, and because it is far from the plane of the Milky Way, which minimizes the tidal force.
Most open cluster lie near or within the Milky Way as seen from here on Earth, but M44 and M67 are about 30 degrees away from the galactic plane. However, the reasons are quite different for the two clusters. M44 appears far from the Milky Way because of perspective; we are very close to M44, so its relatively modest absolute distance from the Milky Way seems large to our eyes. M67 is at least four times more distant, so the actual distance from the plane of the Milky Way is at least four times greater.
Although M67 is very rich, all of its stars are fairly faint, which causes it to show poorly in small instruments under bright skies. From the city, it is just barely visible with averted vision through my 7×35 binoculars, and it is also very difficult in my 70mm scope at low powers. It does better in the 70mm scope at 60X, showing 5 faint stars with direct vision and another 10 or so with averted vision. The cluster is far more impressive from the city in my 178mm scope at 120X, showing some 30 stars, and promising more with averted vision. The brightest stars are arranged in an arrowhead pointing E. Not surprisingly, they are all red giants, although none is bright enough for the color to be apparent in either of my telescopes.
M67 shows much better from the suburbs, where its faint stars merge into a nebulosity that stands out well in my 7×35 binoculars, and provides a lovely backdrop to the view in my 70mm scope. The 178mm scope at 120X resolves about 60 stars in a 20′ circle, a very impressive view.
In good suburban skies, M67 is very easy to locate off alpha Cancri two degrees directly to the east. In all but the worst urban skies, it can be located off the head of Hydra six degrees to the south. Alternatively, you can star-hop from M44, if you happen to be there already.