Enjoying EarthSky? Subscribe.

254,335 subscribers and counting ...

Where’s the moon? 1st quarter

It officially comes on July 1, but, if you live in the Americas, watch for a nearly 1st quarter moon on the evening of June 30. It’ll appear half-illuminated and near Jupiter!

Our friend Patrick Casaert of the Facebook page La Lune The Moon caught the moon on May 1, 2017, when it was nearly 1st quarter.

The moon reaches its first quarter phase on July 1, 2017 at 0:51 UTC. At North American time zones, the moon’s first quarter phase happens on June 30, at 9:51 p.m ADT, 8:51 p.m. EDT, 7:51 p.m. CDT, 6:51 p.m. MDT 5:51 p.m. PDT and 4:51 p.m. AKDT.

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

The Earth and moon are like mirrors to each other. If you were on the moon tonight, you’d see a last quarter Earth. Simulation of last quarter Earth as viewed from 1st quarter moon (2017 July 1 at 0:51 UTC). The terminator or shadow line represents Earth’s line of sunsets. Image via Fourmilab.

There will be a magnificent pairing of the first quarter moon and Jupiter as darkness falls on June 30. This planet ended its retrograde motion on June 10 and is now past its best time for viewing in 2017. But it’s the biggest planet in our solar system, and still dazzlingly bright!

Watch for the first quarter moon and Jupiter on June 30, 2017. Read more.

At quarter moon, the moon’s disk is half-illuminated by sunlight and half-immersed in the moon’s own shadow.

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!

Here’s what a first quarter moon looks like. The terminator line – or line between light and dark on the moon – appears straight. Aqilla Othman in Port Dickson, Negeri Sembilan, Malaysia caught this photo on May 3, 2017. Notice that he caught Lunar X and Lunar V.

Here’s a closer look at Lunar X and Lunar V. Photo taken May 3, 2017 by Izaty Liyana in Port Dickson, Negeri Sembilan, Malaysia. What is Lunar X?

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.

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

MORE ARTICLES