1st quarter moon is May 11-12

The 1st quarter moon comes on May 12 at 1:12 UTC. At European and American time zones, you’ll find it high up at sunset on May 10 and 11. It appears nearly or completely half-illuminated, like half a pie.

Half of the moon.

Nearly first quarter moon from Suzanne Murphy in Wisconsin.

The moon reaches its first quarter phase on Sunday, May 12, 2019, at 1:12 UTC. Although the first quarter moon comes at the same instant worldwide, the clock reads differently by time zone. At North American and U.S. times zones, the first quarter moon actually happens on Saturday, May 11, at 22:12 (10:12 p.m.) Atlantic Daylight Time, 21:12 (9:12 p.m.) Eastern Daylight Time, 20:12 (8:12 p.m.) Central Daylight Time, 19:12 (7:12 p.m.) Mountain Daylight Time, 18:12 (6:12 p.m.) Pacific Daylight Time, 17:12 (5:12 p.m.) Alaskan Daylight Time and 15:12 (3:12 p.m.) Hawaiian Standard Time.

A first quarter moon rises around noon and sets around midnight. You’ll likely spot it in late afternoon or early evening, high up in the sky. At this moon phase, the moon is showing us precisely half of its lighted half. Or you might say that – at first quarter moon – we’re seeing half the moon’s day side.

We call this moon a quarter and not a half because it is one quarter of the way around in its orbit of Earth, as measured from one new moon to the next. Also, although a first quarter moon appears half-lit to us, the illuminated portion we see of a first quarter moon truly is just a quarter. We’re now seeing half the moon’s day side, that is. Another lighted quarter of the moon shines just as brightly in the direction opposite Earth!

And what about the term half moon? That’s a beloved term, but not an official one.

Read more: 4 keys to understanding moon phases

Band of mountains on moon with a few large craters.

Tom Wildoner wrote: “One of my favorite areas to photograph on the moon near the 1st quarter! I captured this view of the sun lighting up the mountain range called Montes Apenninus. The moon was casting a nice shadow on the back side of the mountains. This mountain range is about 370 miles (600 km) long with some of the peaks rising as high as 3.1 miles (5 km).”

Half of the moon with labeled features along straight edge.

Here’s something else to look for on a 1st quarter moon. Aqilla Othman in Port Dickson, Negeri Sembilan, Malaysia, caught this photo. Notice that he caught Lunar X and Lunar V. These are similar features on the moon that fleetingly take an X or V shape when the moon appears in a 1st quarter phase from Earth.

Closeup of boundary between light and dark areas of the moon.

Here’s a closer look at Lunar X and Lunar V. Photo by Izaty Liyana in Port Dickson, Negeri Sembilan, Malaysia. What is Lunar X?

Bottom line: The first quarter moon comes on May 12 at 1:12 UTC; translate UTC to your time. As viewed from the whole Earth, it’s high up at sunset on May 11, looking like half a pie.

Check out EarthSky’s guide to the bright planets.

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Deborah Byrd