1st quarter moon is November 4

The 1st quarter moon arrived on Monday, November 4, 2019, at 10:23 UTC. You’ll find the moon high up at sunset on this evening, appearing half-illuminated, 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 as night came to his part of the world on November 4, 2019. He wrote: “The moon has reached 1st quarter and is visible on my side of the planet now.”

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

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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).”

Half of the moon with Lunar V, Albategnius, and Lunar X labeled 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 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?

Bottom line: The moon reaches its first quarter phase on Monday, November 4, 2019, at 10:23 UTC. As viewed from the whole Earth, it’ll be high up at sunset on this Monday evening, looking like half a pie.

Check out EarthSky’s guide to the bright planets.

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Deborah Byrd