Messier 73 is one of the most unusual entries in the Messier catalog. Unlike the glittering star clusters and sprawling nebulae that fill much of the list, M73 is simply a tiny asterism of four faint stars arranged in a delicate “Y” shape. At first glance, it may not seem like much, but its history makes it worth a closer look.
When Charles Messier cataloged M73 in 1780, he described it as a “cluster of three or four small stars, which appear surrounded by a very faint glow of nebulosity.” With the modest telescopes of his time, faint stars often blurred together, especially when viewed from Paris where Aquarius sits low in the sky. It’s likely that Messier thought he was seeing an unresolved open cluster or even a faint nebula, and so he included it to prevent confusion with comets. We now know it is none of these -- merely an apparent grouping of unrelated dim stars.
In modern telescopes, M73 reveals itself as no more than a handful of faint points. Small instruments show the four stars dimly, while larger apertures sharpen the view and make the “Y” shape stand out more clearly. Its charm is not in grandeur but in context — as one of the catalog’s curious “oddballs” and as a stepping stone between two of Aquarius’s finest deep-sky sights.
What makes M73 especially enticing is its placement at the heart of a remarkable trio. Just a short nudge to the west lies Messier 72, a faint but rewarding globular cluster, while a similar hop to the east reveals the Saturn Nebula (NGC 7009), one of the most striking planetary nebulae in the heavens. Observing all three together offers a delightful variety: a cluster of ancient stars, a glowing planetary nebula shaped like a tiny planet, and a simple but elegant star asterism.
M73
Rating: 🟢 Solid Catch
Level: 🟢 Moderate
How:
When: Aug - Nov
🌟 A Historical Curiosity Charles Messier included M73 in 1780 because it appeared to him as a nebulous cluster. With the limited optics of the time, the faint stars seemed to blend into a haze, and he cataloged it to avoid confusion with comets. Observing it today connects you directly with the history of astronomy and the limitations of early telescopes.
🌟 A Simple Beauty Though it lacks grandeur, M73 has a quiet elegance. Its four stars form a delicate, geometric pattern that stands out once you find it. Many observers find charm in its minimalism — it feels like a secret tucked away in the Messier list.
🌟 Part of an Aquarius Trio M73 gains much of its appeal from its neighborhood. It sits just west of the faint globular cluster Messier 72 and east of the striking Saturn Nebula (NGC 7009). Observing all three in a single session gives you a variety of deep-sky sights: a planetary nebula, a globular cluster, and an odd little asterism.
🌟 A Trophy for Completists For anyone attempting the Messier Marathon or trying to complete the full catalog, M73 is one of the trickier entries. Its faintness makes it easy to overlook, but checking it off brings satisfaction and a sense of accomplishment.
Since M73 lies roughly halfway between the Saturn Nebula and M73, the best way to find M73 is to first find one of these. Neither is easy to find -- the Saturn Nebula is brighter but smaller, while M72 is larger but dimmer. The steps below use M72 as the starting point since it may be slightly easier to find.
Find the Great Square of Pegasus and notice the lower-right star, Markab (+2.49).
Star hop 5 times: to Homam (+3.42), Baham (+3.52), Sadalmelik (+2.94), Sadalsuud (+2.89) and, finally, Albali (+3.76). These are easily visible to the naked eye under most skies.
With your telescope finder, point to Albali and center it. Using either a finder or a low-powered eyepiece, hop 3° south to HR 7976 (+5.86). M72 is less than 1° east. In a low-powered eyepiece, Messier 72 will appear as a small, faint, round haze against the sparse star field of Aquarius. Finally, look 1.2° to the east for M73 and its tiny “Y”-shaped asterism of four stars. Go another 1.8° to the northeast for the Saturn Nebula.
M73
✅ Seek Dark Skies Because the stars of M73 are faint, light pollution can make the asterism difficult to pick out. Under darker skies, the pattern is clearer and the trio of objects in Aquarius is much more satisfying.
✅ Start with the Saturn Nebula or M72 M73 sits about halfway between the Saturn Nebula and M72. First find one of them and then nudge your scope a short about 1.5 degrees to land at M73.
✅ Use Low Power to Identify the Pattern At first glance, M73 is just four faint stars. A wide-field, low-power eyepiece makes the “Y”-shaped arrangement stand out more clearly against the background sky.
✅ Manage Your Expectations Remember that M73 is not a true cluster or nebula but a simple asterism. The pleasure comes from recognizing its pattern and appreciating its odd inclusion in Messier’s catalog.
✅ Pair It with Neighbors Don’t view M73 in isolation. Sweep slightly west to capture Messier 72, a faint globular cluster, and then back east to revisit the Saturn Nebula. Together, they make an excellent mini-tour of Aquarius.
M73
❌ Naked Eye
To the naked eye, Messier 73 is invisible. Its faint stars are too dim to separate themselves from the backdrop of Aquarius, leaving no hint of its presence without optical aid.
⚠️ Binoculars
In binoculars, M73 is extremely subtle. Under dark skies it may appear as a tiny grouping of faint points, but the pattern is not immediately obvious. Most of the time it comes across as just another handful of dim field stars.
✅ Small Telescope
Through a small telescope, the asterism becomes recognizable. The four stars form a delicate “Y” shape, though they remain faint and unimpressive compared to true clusters. Still, the pattern is distinct enough to make identification rewarding.
✅ Medium Telescope
A medium telescope sharpens the view and makes the faint stars stand out more confidently against the background. The asterism’s geometry becomes easier to appreciate, and its placement near M72 and the Saturn Nebula adds to its appeal.
✅ Large Telescope
In a large telescope, M73 does not transform the way most Messier objects do, since it is simply a chance alignment of stars. The view remains four faint points, though with more brightness and clarity.
M73
Messier 73 is a faint asterism of four stars, so its visibility depends heavily on sky darkness. Unlike nebulae or clusters, there is no haze or glow — just a subtle pattern of dim points that can easily be lost in brighter skies.
🟣/🔵 In Bortle 1–2 skies, M73 is easy to spot once located. The four stars stand out clearly, and the delicate “Y”-shaped pattern is immediately recognizable. It looks simple but distinct against the sparse Aquarius background.
🟢 In Bortle 3–4 skies, the asterism remains visible but less obvious. The stars are fainter, and while the “Y” pattern can still be made out, it requires a bit more concentration to see it cleanly.
🟡/🟠 In Bortle 5–6 skies, M73 becomes a real challenge. The stars blur into the background, and the asterism is difficult to separate from the surrounding field. Observers may see only one or two of the stars without effort.
🔴 In Bortle 7+ skies, M73 is effectively lost. Its faint points vanish into the skyglow, and the pattern is nearly impossible to recognize. Only the largest telescopes under these conditions will tease it out, and even then it is unimpressive.
M73
DSOs within 48° or 2 outstretched hands at arm's length
M73 - A Curious Little Asterism
Find the Great Square of Pegasus and notice the lower-right star, Markab (+2.49).
Star hop 5 times: to Homam (+3.42), Baham (+3.52), Sadalmelik (+2.94), Sadalsuud (+2.89) and, finally, Albali (+3.76). These are easily visible to the naked eye under most skies.
With your telescope finder, point to Albali and center it. Using either a finder or a low-powered eyepiece, hop 3° south to HR 7976 (+5.86). M72 is less than 1° east. In a low-powered eyepiece, Messier 72 will appear as a small, faint, round haze against the sparse star field of Aquarius. Finally, look 1.2° to the east for M73 and its tiny “Y”-shaped asterism of four stars. Go another 1.8° to the northeast for the Saturn Nebula.
