July's Last Quarter Moon Is Coming This Weekend

If you scan the sky after the sun sets this Sunday, July 12, you’ll see this month’s last quarter moon. And if you’re a novice sky-gazer, you might be surprised to find that half—not a quarter—of the moon is illuminated.

The name isn’t related to how much of the moon is visible, but rather, which phase of its monthly orbit around Earth it’s currently in. The Old Farmer’s Almanac suggests picturing the cycle like a baseball diamond: A new moon (which you can’t see at all) is home plate; a first quarter moon is first base; a full moon is second base; and a third (or last) quarter moon is third base. In other words, the last quarter moon marks the last quarter of the cycle before we get another new moon. And since we can see half of it, it’s sometimes colloquially called a half moon.

As EarthSky reports, July’s last quarter moon hits its peak at 7:29 p.m. EDT on Sunday night, but you can wait until the sky gets darker for a clearer view. Though it’s not the last last quarter moon of the year, this one is extra special. Since it peaks just four hours after the lunar apogee—the point in the moon’s orbit when it’s farthest from Earth—July’s last quarter moon will be farther from the Earth than any other quarter moon this year.

It won’t appear noticeably dimmer or more distant to the naked eye, but it’s still a cool fact to mention to whomever happens to be around on Sunday night. On the following nights, you can watch the waning crescent grow slimmer and slimmer until the moon disappears completely on July 20 and starts the cycle over again.

[h/t EarthSky]