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Mega Moon Puts on a Show on March 19

Super moon update: In case you missed it, REI colleague Todd Kurtz shared a photo he took of the super perigee moon March 19 as it rose above the peaks of the Cascades, with the port of Seattle in the foreground. (See Todd's photo at the bottom of this post.) Skies can be fickle, but we hope lots of people got a chance to enjoy the spectacle in person. The next super perigee moon is due to appear in 2029. Here's our original post on the topic:

Prepare to get mooned in a big way Saturday night. The largest full moon since 1993 will rise in the east at sunset on March 19.

If the skies cooperate in your region, you can see something known as a super perigee moon. As explained in this NASA Science News report, the moon orbits earth in an elliptical, oval-shaped pattern. During the shorter phase of its orbit, at perigee, the moon is roughly 31,000 miles closer to earth than during its longer, more distant phase (apogee). Accordingly, the moon at perigee looks approximately 14% larger and 30% brighter than at apogee.

I spoke with Geoff Chester, the U.S. Naval Observatory official quoted in the NASA Science News article. (He's also an REI member.) He explained that an "astronomical full moon" is the moment when the moon is exactly 180 degrees from the sun with the earth in between—though not on the same plane as the sun and moon. That's when a lunar eclipse occurs. At perigee, the moon's elliptical orbit around earth puts it a little higher or lower than the earth's relationship to the sun.

"Essentially, a full moon occurs when the moon is exactly opposite the sun in the sky," says Chester, a pubic affairs officer with the USNO in Washington, D.C. "People generically refer to 'full moon' as the time when the moon looks full, which when viewed with an unaided eye can last for a period of about 24 hours. But it is an astronomically defined moment."

On Saturday the moon will be astronomically "full" 59 minutes before perigee (when the moon draws closest to earth during its orbit). The last time the 2 events so closely intersected was the perigee moon of March 8, 1993, when the difference was 72 minutes. Between then and Saturday night, the next closest time to perigee that the moon reached fullness was Dec. 22, 1999 (5 hours before perigee) and Dec. 12, 2008 (6 hours after perigee).

Some sharp-eyed viewers, such as my REI colleague Peter Newton—a senior designer and a 3-time U.S. Olympic competitor in sprint kayaking—noticed a reference to a March 28, 1983 perigee moon in the video that accompanies this report. That indeed was a super perigee moon, but it's not the most recent.  The March 8, 1993 full moon gets that designation.

We're all about accuracy here at The REI Blog. Thanks, Peter.

Viewing tip: For maximum visual impact Saturday night, watch for the moon as it emerges above the horizon in your area. If photographing the moment, try including an earthbound object in silhouette—a tree or building—for perspective.

Lots of opinions circulate around full moons. Do you think they have influence on events or behavior on earth? I'm not in that camp, but how about you? What unusual activity have you attributed to a full moon?

Note: This post contains revised infomation included after its original publication. Photo below by Todd Kurtz.

Posted on at 3:18 PM

Tagged: Full Moon, NASA, apogee, moon and perigee

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