EarthSky.org
Tonight – May 10 – the moon is full. Here’s something fun about this May full moon, and, in fact, about most full moons. That is, it won’t undergo an eclipse. In fact, the May 10 full moon swings a whopping five degrees (10 moon diameters) north of the ecliptic, the plane of Earth’s orbit around the sun.
So it misses being in Earth’s shadow by a wide margin.
Some full moons come closer to passing through Earth’s shadow – that is, closer to being in eclipse without actually doing so – but the fact is that most full moons fail to reside at the antisolar point, the point that’s directly opposite the sun.
It’s only when the moon passes through or very close to the antisolar point that we see a total eclipse of the moon.
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| Worldwide map via Earthview, showing the day and night sides of Earth at the instant of the May full moon, May 10 at 2:42 p.m., Bonners Ferry time. |
The next two full moons – June and July 2017 – will pass to the north of the ecliptic and the antisolar point, too. So there will be no lunar eclipse in June or July 2017.
The August 2017 full moon will sweep less than one degree north of the ecliptic. The relatively close pass will bring the southern part of the lunar disk into the northern part of the Earth’s dark umbral shadow. So, if you’re on the right place on Earth, you’ll see a partial lunar eclipse on August 7, 2017.
It’ll come just two weeks before the much-anticipated total solar eclipse of August 21, 2017, first total solar eclipse to be viewed from the contiguous United States since 1979.
This May full moon is the second full moon after the March equinox. In North America, we’ll call it the Flower Moon, Planting Moon or Milk Moon. Meanwhile, in the Southern Hemisphere, this full moon is called the Beaver Moon or Frost Moon.
For general reference, we can say the moon is full all night. But, technically speaking, the moon is full only at the instant that it’s 180-degrees from the sun in ecliptic longitude. The moon turns full on May 10 at 21:42 UTC (2:42 p.m. Bonners Ferry time).
For North America, the moon will turn exactly full when the sun is above the horizon and the moon is still below it.
Because the moon stays more or less opposite the sun in our sky at the vicinity of full moon, tonight’s moon will rise in the east around sunset and climb highest up for the night around midnight (midway between sunset and sunrise). That’s true as seen from around the globe.
Then, around sunrise on May 11 – as seen from around the world – the moon will set in the west.