Enjoying EarthSky? Subscribe.

172,353 subscribers and counting ...

First of 3 full supermoons on August 29

Contrasting a full supermoon (full moon at perigee) with a micro-moon (full moon at apogee). Image credit: Stefano Sciarpetti

Tonight is Aug 29, 2015

Moon Phase Courtesy U.S. Naval Observatory

Supermoon weekend! The full moon of August 29, 2015 is the first of this year’s three full supermoons. It’s a full moon near perigee, or near its closest point to Earth for the month. Like it or not, modern skylore dictates that these sorts of moons are called supermoons.

Image at top shows a micro-moon (smallest full moon) superimposed on supermoon (largest full moon). This image – an Astronomy Picture of the Day – is from Stefano Sciarpetti.

But will your eye see that the moon is bigger on the night of August 29? Well … it depends. Are you an incredibly careful observer? Have you watched the full moon over a period of months, leading up to now? If so, says Daniel Fischer in Königswinter, Germany, you can discern the extra-large size of the supermoon using just your eye. Read Daniel’s article on this subject.

The closest and largest full supermoon of them all will fall on September 28, to stage a total eclipse of the moon. Some will call it a Blood Moon eclipse.

In North America, we often call the August full moon the Sturgeon Moon, Corn Moon or Grain Moon. The August 2015 full moon is also the first of three full-moon supermoons in 2015. Previously, we had three new moon supermoons in January, February and March, 2015. The full moons on August 29, September 28 and October 27 all enjoy the supermoon designation because the centers of these full moons and the center of Earth are less than 361,836 kilometers (224,834 miles) apart. The closest supermoon of the year comes with the September 28 full moon, presenting a moon that’s only 356,877 kilometers (221,753 miles) from Earth.

Details on the August, 2015 full supermoon

The full moon mirrors sun’s path for six months hence

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Super cool super-moonrise composite from Fiona M. Donnelly in Ontario.  This was the supermoon of August, 2014.

Super cool super-moonrise composite from Fiona M. Donnelly in Ontario. This was the supermoon of August, 2014.

Details on the August, 2015 full supermoon The full moon falls at the same instant all over the world: August 29 at 18:35 Universal Time.

Clock time for this full moon – and every full moon – varies by time zone. For London, the moon turns full at 7:35 p.m. BST on August 29, at which time the afternoon sun shines in the west and the moon has not yet risen in the east. For the U.S., the moon turns full at 1:35 p.m. CDT on August 29, when the sun shines way up high and the moon lies on the other side of the world, beneath our feet.

Technically speaking, the moon turns full at the instant that the moon lies most opposite the sun for the month. Because the moon stays more or less opposite the sun throughout the night, watch for a full-looking moon in the east at dusk, highest in the sky around midnight and low in the west at dawn. On the nights immediately before and after full moon, the moon still looks plenty full to the eye.

When is perigee, the moon’s closest point to Earth? In August, 2015, the moon’s perigee comes less than one day after full moon, on August 30 at 15:24 Universal Time.

The close coincidence of full moon and perigee makes this August full moon a supermoon.

By the way, no particular effects are expected from this extra-close full moon … unless you have the mass of an ocean! In that case, gravity will come into play. In other words, because it’s a supermoon, and relatively close to Earth, this month’s full moon will pull harder than usual on Earth’s oceans. Expect higher-than-usual tides to follow this full moon by a day or so.

August 10, 2014 supermoon over Loutraki, Greece by Mellissa Briley.

August 10, 2014 supermoon over Loutraki, Greece by Mellissa Briley.

The full moon mirrors sun’s path for six months hence. By the way, any full moon mirrors the sun’s path across the sky for six months hence.

And so here’s another cool thing you can notice about the August 29 full moon. As seen from the Northern Hemisphere, this full moon will follow the rather low path of the late winter sun. As viewed from southerly latitudes, the moon will follow the loftier path of the late summer sun.

Enjoy moon-watching tonight and Sunday night!

Day and night sides of Earth at instant of August 2015 full moon (2015 August 29 at 18:35 Universal Time).

Day and night sides of Earth at instant of August 2015 full moon (2015 August 29 at 18:35 Universal Time).

Bottom line: The full moon on August 29 ushers in the first of three full-moon supermoons in 2015. Full moon is August 29, 2015, at 18:35 Universal Time. The moon’s perigee or closest point comes on August 30, at 15:24 Universal Time.

Read more: What is a supermoon?