For one brief stretch each spring, amateur astronomers attempt one of backyard astronomy’s most ambitious challenges: spotting an entire catalog of deep-sky objects in a single night. Known as the Messier Marathon, the quest requires observers to locate all 110 Messier objects—from galaxies to star clusters to nebulae—between dusk and dawn.

The feat is only possible for a short window in late March or early April, when Earth’s position allows all of the catalog’s objects to appear in the night sky over the course of a single night. In 2026, the marathon runs from March 14-22. For dedicated stargazers, it’s both a test of endurance and a celebration of some of the most spectacular sights in the night sky. Here’s what you need to know.

What are Messier objects?

The challenge revolves around a catalog of celestial objects compiled more than two centuries ago by French astronomer Charles Messier. His 1774 Catalogue des Nébuleuses et des Amas d’Étoiles was essentially “a cosmic ‘do not fly’ list of 110 objects he found annoying because they could be mistaken for the comets he was actually hunting. Today, this catalogue is the amateur astronomer’s ultimate scavenger hunt.

The Messier catalog includes some of the most famous deep-sky objects visible from Earth, each designated by the letter M followed by a number. Among them are the Andromeda Galaxy (M31), the nearest large galaxy to the Milky Way; the Orion Nebula (M42), a glowing stellar nursery visible within Orion’s Belt; and the Pleiades (M45), an open star cluster of blue stars often called the Seven Sisters.

(Here are 10 weird things you (probably) didn’t know about the Milky Way.)

Most Messier objects can be seen with modest backyard telescopes or even binoculars under dark skies—and some, like the Orion Nebula, are bright enough to be seen with the naked eye.

What is the Messier Marathon?

That catalog eventually inspired one of amateur astronomy’s most demanding observing challenges. Completing the marathon used to be significantly harder before the invention of digital sky maps and “GoTo” telescopes, which have computerized systems that automatically locate and point toward celestial targets, says Gallaway.

In the past, the marathon was an exercise in ‘star-hopping,’ a slow, meditative, and often frustrating crawl across paper star charts, and many never completed a full Messier Marathon. You need free time and much better equipment, including two smart and three robotic telescopes.

Even with GoTo telescopes—which some amateur astronomers might consider cheating—completing the marathon requires careful planning and stamina. Observers must begin immediately after sunset to catch objects setting in the west, continue scanning the sky as new targets rise in the east throughout the night, and adjust to real-time complications such as cloud cover.

Why the Messier Marathon happens in March or April

Observing all 110 objects in a single night is only possible between mid-March and early April.

By a stroke of orbital coincidence, there is a window in March where the sun sits in a lonely patch of sky, allowing an observer to see all 110 objects in a single dusk-to-dawn sprint. Part of this would have been caused by Messier’s location in Paris and the limits of his instrumentation, but it was also a bit of dumb luck.

In practical terms, this means the sun’s position at this time of year prevents the Messier objects from being obscured by daylight, as they are the rest of the year.

Within this window, the best time for a Messier Marathon is during a new moon, when the absence of moonlight makes faint galaxies, nebulae, and star clusters easier to spot.

How to attempt the Messier Marathon

For those tempted to try the challenge themselves, preparation is key. No central organization oversees the Messier Marathon, but observatories and local astronomy groups often host Messier Marathon events. Join your local astronomy group. There are groups all over the world. If they are doing the Messier Marathon, they will always welcome more hands.

But if you’re hoping to take on the challenge alone, here’s how to get started.

First, consider your geographic location. The full Messier Marathon is primarily a Northern Hemisphere event. Because Messier compiled his catalogue from Paris, some objects sit too far south to be easily seen from many Southern Hemisphere locations. Observers in high northern latitudes might not be able to see all 110 objects, either. Many stargazers instead attempt a “mini” Messier Marathon, focusing on the objects visible from their location.

Next, choose an observation site with wide, unobstructed views of the horizon. Depending on your latitude, some Messier objects will appear low in the sky, so open landscapes—such as fields, hilltops, or beaches—offer the best vantage point. Avoid light pollution whenever possible.

Planning the order of observations is also key, since not all Messier objects will be visible all night. Try to get the objects in the west done first before they set.

Finally, start early. Set up well before the sun goes down and start trying to image your first target at twilight. You might not see it because of the twilight sky, but as soon as you can, move to the next target.”