There’s something magical about looking up at the night sky and realizing you’re seeing light that has traveled for tens of thousands of years just to meet your eyes. Tonight, we’re going to explore one of the crown jewels of amateur astronomy: Messier 13, also known as the Great Hercules Cluster. Whether you’re new to stargazing or have already worn out a few star charts, M13 is a must-see target that will leave you in awe.
Grab your telescope (or even just your binoculars), a comfy lawn chair, and a jacket if it’s chilly — let’s dive into the wonders of M13!
What is Messier 13?
Messier 13 is a globular cluster — a dense, spherical collection of hundreds of thousands of stars bound tightly by gravity. It lies about 22,000 to 25,000 light-years away from Earth, in the constellation of Hercules. It’s roughly 145 light-years across, which makes it one of the largest and brightest globular clusters visible from the Northern Hemisphere.
It was first cataloged by Charles Messier in 1764, who was busy creating a list of “nuisance” objects that could be mistaken for comets. Little did he know he was also compiling a greatest-hits list for amateur astronomers centuries later.
Fun fact: In 1974, the Arecibo Observatory beamed a radio message toward M13 in an attempt to contact extraterrestrial life. The thought being, if you’re going to call out into the cosmos, why not aim for one of the biggest gatherings of stars nearby?
What Makes M13 Special?
When you look at M13 through a telescope, you’re seeing something ancient and resilient. The stars in a globular cluster like this one are old — around 11.65 billion years, almost as old as the universe itself. They’re like cosmic elders, quietly hanging around the galaxy’s outskirts, orbiting the Milky Way’s center.
What makes M13 particularly stunning is its sheer brightness and compactness. Through a small telescope, it appears like a fuzzy, glittering ball. With a larger telescope or under darker skies, you can start resolving individual stars — little pinpricks of light that shimmer like a spilled bag of diamonds.
Finding Messier 13: A Simple Observation Guide
Finding M13 might sound daunting if you’re new to stargazing, but trust me — with a little patience, it’s absolutely doable. Here’s a basic guide:
Step 1: Find the Constellation Hercules
Season: Best viewed from late spring through early fall. June and July are perfect months.
Location: Northern Hemisphere observers have the advantage here, but it can also be spotted from mid-southern latitudes.
Time: Look around 9 PM to midnight when Hercules is well above the horizon.
Hercules isn’t the most obvious constellation — it’s made up of relatively dim stars — but it’s wedged between two bright constellations, Lyra (home to Vega, one of the brightest stars) and Corona Borealis (the “Northern Crown”).
Step 2: Find the Keystone Asterism
Look for the Keystone, a small trapezoid of four stars that forms Hercules’ “body.”
The stars making up the Keystone are: Pi Herculis, Eta Herculis, Zeta Herculis, and Epsilon Herculis.
The Keystone is your treasure map.
Step 3: Locate M13
M13 is located on the western edge of the Keystone.
Imagine a line connecting the stars Eta Herculis and Zeta Herculis — M13 is slightly closer to Eta.
With binoculars (around 7×50 or 10×50), you might see a faint smudge.
With a small telescope (60mm or more), it will appear as a bright, hazy ball.
With a larger telescope (6-inch or more), you can resolve dozens, if not hundreds, of tiny stars.
Pro tip: Use averted vision — don’t look directly at M13, but slightly to the side. Your peripheral vision is more sensitive to faint light, and the cluster will seem to pop into view!
Tips for a Great Observation Night
Dark Skies Are Key: The darker your location, the better. M13 is bright enough to punch through moderate light pollution, but you’ll get the best views under a truly dark sky.
Let Your Eyes Adjust: It takes about 20-30 minutes for your eyes to fully adapt to the dark. Avoid looking at your phone or bright lights.
Start Low, Then Zoom In: Use a low-power eyepiece first to locate the cluster, then switch to higher magnification to resolve more stars.
Steady Your Binoculars: If you’re using binoculars, try stabilizing them against a wall, tree, or use a tripod for best results.