1st quarter moon is April 1

The 1st quarter moon happens on April 1, 2020, at 10:21 UTC. As viewed from anywhere on Earth, a 1st quarter moon is at its highest in the sky at sunset, looking like half a pie.

A precisely half-illuminated moon with a dotted line dividing the halves.

View at EarthSky Community Photos. | Our friend Dr Ski in the Philippines caught this photo of a 1st quarter moon on November 4, 2019. Thanks, Dr Ski!

A first quarter moon rises around noon and sets around midnight. You’ll likely spot it in late afternoon or early evening, when it’s at its highest 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.

Half of the moon with tiny labeled X and V shapes along straight edge.

Lunar X and Lunar V appear when the moon is near its 1st quarter phase. They aren’t really Xs and Vs on the moon. They’re just high areas, catching sunlight, creating an example of pareidolia on the moon. Aqilla Othman in Port Dickson, Negeri Sembilan, Malaysia, caught them both in May of 2017. Notice that he caught Lunar X and Lunar V.

Closeup of boundary between light and dark areas of the moon with Lunar V and X labeled.

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?

Telescopic closeup of 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).”

Bottom line: The next 1st quarter moon will come on April 1, 2020, at 10:21 UTC. As viewed from anywhere on Earth, a 1st quarter moon is at its highest in the sky at sunset, looking like half a pie.

Check out EarthSky’s guide to the bright planets.

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Deborah Byrd