The half-lit moon is upon us! Here’s what to expect when Earth’s natural satellite reaches its third quarter phase early on March 11, how to see it and what to look for on its ancient surface.
March third, or last quarter moon phase will take place at 5:39 a.m. EDT (0939 GMT), which the moon appear in Earththe sky with the left half illuminated by direct sunlight and the right masked in shadow, close stars of the constellation Scorpius.
Viewers in the US will see the half-illuminated moon shining low on the southern horizon at this time, with the red supergiant star Antares glows about 10 degrees in the 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, the nights around third quarter phase are a wonderful time to observe the vast expanse of the Mare Imbrium (Self of Showers) – a 700-mile-wide (1,127-kilometer-wide) impact site that dominates the upper-left area of the lunar hemisphere (as seen from the north).
The dark expanse we see today is the remains of ancient lava flows that filled the basin in the wake of its creation nearly 4 billion years ago, before solidifying to renew part of the moon’s surface.
Sweep a 6-inch telescope across the line that separates night from darkness — known as the terminator — just above the lunar equator to find the Montes Apennines mountain range that bends from the shadowy to the sunlit side of Earth’s satellite. The 370-mile (600 km) geographic feature forms the southeastern border of Mare Imbrium and will make a lovely target in the early hours of March 11 when sunlight catches the 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 you can cross your telescope over the colossal shadow shape of Copernicus Crater and explore the shadowed western rim and central peaks – the tallest of which is about a kilometer high – before turning your binoculars to Mare Imbrium’s northwestern rim.
Here lies the Sinus Iridum, Rainbows Bar, another huge crater bordering the 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 captures the upper peaks while leaving the surrounding terrain in shadow.
Over the coming week, the moon’s sunlit area will become increasingly smaller, transforming from a hemisphere to a waning crescent, before finally disappearing from our view entirely as it slips into the glare of our parent star on the nights around it new moon phase 18 March.
Want to explore the ever-changing face of the moon as it makes its 27-day journey around Earth? So be sure to check out our picks best telescopes — and smart telescopes — available in 2026. If you are a photographer, you can also read our summaries of top cameras and lenses for astrophotographytogether with ours guide to photographing the surface of the moon!
Editor’s note: If you would like to share your moon photos with Space.com readers, please send photos, names and comments, along with the time and location of the photo shoot to spacephotos@space.com.
