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First quarter moon comes January 5

A first quarter moon rises at noon and is highest at sunset. Next full moon is January 12 at 11:34 UTC.

Karl Diefenderfer in Quakertown, Pennsylvania caught the moon on the evening of January 4, 2017, when it was nearly a first quarter moon.

A first quarter moon shows half of its lighted hemisphere – half of its day side – to Earth.

First quarter is January 5, 2017 at 19:47 UTC. It’s a waxing moon, in the sky each evening when the sun goes down. Next full moon is January 12 at 11:34 UTC.

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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 the moon appears half-lit to us, it’s good to recall that the illuminated portion of a first quarter moon truly is just a quarter. On the night of first quarter moon, we see half the moon’s day side, or a true quarter of the moon. 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.

A first quarter moon rises at noon and is highest in the sky at sunset. It sets around midnight. First quarter moon comes a week after new moon. Now, as seen from above, the moon in its orbit around Earth is at right angles to a line between the Earth and sun.

When the first quarter moon sets around midnight, the sun is below your feet. See? Good time to get a 3-D sense of the moon as a world in space, always half-illuminated by the sun. Animation created from images of setting first quarter moon, June 12, 2016, by Peter Lowenstein in Mutare, Zimbabwe.

When the first quarter moon sets around midnight, the sun is always below your feet. Good time to experience the moon and Earth as worlds in space, always half-illuminated by the sun. Setting first quarter moon by Peter Lowenstein in Mutare, Zimbabwe.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

Deborah Byrd

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