Who was Charles Messier?

Charles Messier was a French astronomer who lived from 1730 to 1817. He was most active in the late 1700s and was known for his passion for hunting comets. During his time, comets were exciting discoveries, and Messier wanted to find as many as possible. He used a 100 mm refracting telescope to search the skies.

What is the Messier Catalogue?

While searching for comets, Messier often came across fuzzy objects that didn’t move across the sky like comets did. To help himself and other astronomers avoid confusion, he began documenting these objects. This list became known as the Messier Catalogue.

The catalogue is comprised of 110 deep-sky objects such as galaxies, nebulae, and star clusters. These objects are some of the most famous and beautiful sights in the night sky. Messier’s work helped future astronomers by providing a clear list of objects that were not comets but amazing astronomical targets that are still very much worth observing. Today, the Messier Catalogue is one of the most well-known guides for amateur and professional astronomers alike.

Some of the most famous Messier objects pictured above include:

• M13 – The Great Hercules Cluster: A bright and dense globular cluster filled with hundreds of thousands of stars.
• M31 – The Andromeda Galaxy: The nearest major galaxy to the Milky Way, visible to the naked eye under dark skies.
• M33 – The Triangulum Galaxy: A spiral galaxy that is part of our Local Group and often seen in dark-sky locations.
• M42 – The Orion Nebula: One of the brightest nebulae in the sky, a stellar nursery where new stars are forming.
• M45 – The Pleiades: Also known as the Seven Sisters, this bright open star cluster is stunning in binoculars.
• M46 & M47 – A pair of contrasting open clusters: M46 contains a fascinating planetary nebula, while M47 has fewer but more prominent stars.
• M65 & M66 – Part of the Leo Triplet: These two spiral galaxies, along with NGC 3628, make for a great deep-space observation.
• M81 & M82 – Bode’s Galaxy and the Cigar Galaxy: A pair of galaxies in Ursa Major that offer a stunning contrast—one a classic spiral, the other a starburst galaxy undergoing intense activity.
• M101 – The Pinwheel Galaxy: A large and beautiful face-on spiral galaxy with well-defined arms, located in Ursa Major.

What is a Messier Marathon?

A Messier Marathon is an exciting challenge where astronomers try to observe all 110 Messier objects in a single night. This is only possible at certain times of the year, and March is the best month for it. March is ideal because of how the Earth’s position in its orbit aligns with the placement of the Messier objects in the night sky. At this time of year, the objects rise and set in a way that allows them all to be seen in one night, given the right conditions. In other months, some objects may be too close to the Sun and become difficult or impossible to observe. Additionally, March offers longer nights, providing enough darkness to complete the challenge before the sky brightens at dawn.

When, Where, and How Should I Marathon?

Dark Skies and the New Moon

While likely obvious, dark skies are a must to complete a Messier Marathon. After all, Charles Messier only had a four-inch refractor to make his discoveries, but he had relatively little light pollution back in the late 1700s. So, to have a successful Messier Marathon, you’ll want to find an observation site with very low light pollution and ideally a new moon. There are two new moons best suited for the marathon this year: February 27th and March 29th. You can check out our article Where to Explore the 2025 Denver Night Skies for suggestions on where to find dark skies throughout Denver and the state of Colorado.

The Denver Astronomical Society (DAS) has chosen two weekends in March that align closely with the dark skies afforded by a new moon to hold Messier Marathon events. These will take place at the Kline-Dodge Dark Sky Site in Deer Trail, where the skies are dark enough to see all the objects clearly. The official marathon dates are February 28–March 2 and March 28–30.

Tips for a Successful Marathon

In addition to the dark skies, you’ll also need a telescope to complete a Messier Marathon, as many of the objects in the catalogue have apparent magnitudes around 9 or 10 making them difficult to see without aid. However, some objects are very bright and can be spotted easily with binoculars or even the naked eye.

1. Pick the Right Location and Night – Choose a site (like the Kline-Dodge Dark Sky Site) with clear horizons and minimal light pollution. Aim for a night when the moon is absent or just a thin crescent, and the sky is free of haze. If the weekends above don’t work for you, try other dates close to the February and March new moons when the moon is a small crescent.
2. Prepare Ahead of Time – Set up your equipment before sunset and use star charts or maps you’re familiar with to navigate the sky efficiently.
3. Follow a Strategic Plan – Have a well-organized schedule to track objects, especially those visible only for a short time at dusk or dawn. See our recommendation for the Marathon Sequence below.
4. Stay Focused and Adapt – If you can’t find an object, try a different approach or reference star. Avoid aimlessly scanning and start fresh if needed.
5. Take Care of Yourself – Get plenty of rest beforehand and bring snacks, warm drinks, and lots of layers of clothing to stay warm and energized throughout the night.

The Sequence

Below is our recommended observation sequence for the Kline-Dodge Dark Sky Site at 39° 38′ 39.1″ N latitude. It starts with M77 and M74, which set early, then moves through the winter sky objects, the Virgo Cluster, and finally the summer objects before dawn, ending with M30. You can also download this list in either a csv (Excel) or skylist (SkySafari) format. If you’d like to create your own sequence, a great resource can be found at Larry McNish’s Messier Marathon Planner.

Targets marked with ☀️ will be difficult to see due to the sunlight and the target’s close position to the horizon. Targets marked with 👀 have bright enough magnitudes to be observed with the naked eye. 

If you’ve never done a Messier Marathon before, this is a great opportunity to challenge yourself and experience the wonders of the night sky just as Charles Messier did over 200 years ago. Join us this March and take part in this amazing astronomical adventure!

Clear skies and happy stargazing marathoning!