The half-lit moon is upon us! Here’s what to expect as Earth’s natural satellite reaches its third quarter phase early on March 11, how to see it and what to look out for on its ancient surface.
March’s third, or final quarter moon phase will occur at 5:39 a.m. EDT (0939 GMT), as the moon appears in Earth‘s sky with its left half illuminated by direct sunlight and its right masked in shadow, close to the stars of the constellation Scorpius.
Viewers in the U.S. will find the half-lit moon shining low on the southern horizon at this time, with the red supergiant star Antares glowing roughly 10 degrees to its upper right — about the width of your clenched fist held at arm’s length to the sky.
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If you’re an early riser, then the nights surrounding the third quarter phase are a wonderful time to observe the sweeping expanse of Mare Imbrium (the Sea of Showers) — a 700 -mile-wide (1,127-kilometer-wide) impact site that dominates the upper-left region of the lunar disk (when viewed from the northern hemisphere).
The dark expanse we see today is the remains of ancient lava flows that filled the basin in the wake of its creation almost 4 billion years ago, before hardening to renew a swathe of the lunar surface.
Sweep a 6-inch telescope across the line separating night from dark — known as the terminator — slightly above the lunar equator to find the Montes Apennines mountain range curving from the shadowed to the sunlit side of the Earth’s satellite. The 370-mile-long (600 km) geographical feature forms the southeastern border of Mare Imbrium and will make for a gorgeous target in the early hours of March 11 as sunlight catches its west-facing peaks and slopes.
By the early hours of March 12, the terminator will have swept past the Montes Apenninus, hiding them from view. Now, traverse your telescope over the colossal shadowed form of the Copernicus crater and explore its shadowed western rim and central peaks — the tallest of which is roughly a kilometer-high — before turning your scope to Mare Imbrium’s northwestern edge.
Here lies Sinus Iridum, the Bar of Rainbows, another enormous crater that borders Mare Imbrium, whose northern edge is formed by the Montes Jura mountain range. The rocky formation creates a spectacular “Golden Handle” effect 10-11 days after each new moon, as sunlight catches its upper peaks while leaving the surrounding terrain in shadow.
Over the coming week, the sunlit region of the moon will become ever smaller, transforming from a half-sphere to a waning crescent, before finally disappearing altogether from our sight as it slips into the glare of our parent star on the nights surrounding its new moon phase on March 18.
Want to explore the ever-changing face of the moon as it makes its 27-day journey around Earth? Then be sure to check out our picks of the best telescopes — and smart telescopes — available in 2026. If you’re a photographer, you may also want to read our roundups of the top cameras and lenses for astrophotography, along with our guide to photographing the lunar surface!
Editor’s Note: If you would like to share your moon photos with Space.com’s readers, then please send your images, name and comments, along with the time and location of your shoot to spacephotos@space.com.
