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Last quarter moon is October 2

Last quarter moon is October 2 at 09:45 UTC. A last quarter moon rises in the middle of the night.

The moon was almost exactly at last quarter when Deirdre Horan in Dublin, Ireland, captured this photo. The terminator line, or line between light and dark on the moon, appears straight.

When the moon appears half-lit in sunshine and half-immersed in the moon’s own shadow – when it rises in the middle of the night – astronomers say it is at last quarter. Before sunrise on April 8, 2018, the moon was at or near its last quarter phase. A last quarter moon always rises in the middle of the night, appears at its highest in the sky around dawn, and sets around midday.

On a last quarter moon, the lunar terminator – the shadow line dividing day and night – shows you where it’s sunset on the moon.

A last quarter moon provides a great opportunity to think of yourself on a three-dimensional world in space. For example, it’s fun to see this moon just after moonrise, shortly after midnight. Then the lighted portion points downward, to the sun below your feet. Think of the last quarter moon as a mirror to the world you’re standing on. Think of yourself standing in the middle of Earth’s nightside, on the midnight portion of Earth.

Also, a last quarter moon can be used as a guidepost to Earth’s direction of motion in orbit around the sun.

In other words, when you look toward a last quarter moon high in the predawn sky, for example, you’re gazing out approximately along the path of Earth’s orbit, in a forward direction. The moon is moving in orbit around the sun with the Earth and never holds still. But, if we could somehow anchor the moon in space … tie it down, keep it still … Earth’s orbital speed of 18 miles per second would carry us across the space between us and the moon in only a few hours.

A great thing about this observation is that it can be done from anywhere, for example, as in the photo below, from large cities.

Ben Orlove wrote from New York City: “I was sitting in the roof garden of my building, and there was the moon, right in front of me. You were right, this is a perfect time to visualize … the Earth’s motion.”

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

New moon
Waxing crescent moon
First quarter moon
Waxing gibbous moon
Full moon
Waning gibbous moon
Last quarter moon
Waning crescent moon

Read more: 4 keys to understanding moon phases

Bottom line: The next last quarter moon is October 2, 2018, at 9:45 UTC; translate UTC to your time.

Deborah Byrd

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