The moon appears full to the eye for two to three nights. However, astronomers regard the moon as full at a precisely defined instant, when the moon is exactly 180 degrees opposite the sun in ecliptic longitude. That full moon instant falls on July 16, 2019, at 21:38 UTC. Translate UTC to your time zone.
This upcoming full moon will undergo a partial lunar eclipse. Unfortunately, North America misses out on this eclipse entirely. The eclipse is visible from South America at early evening July 16. From Europe and Africa, it happens later in the evening July 16. In Asia and Australia, watch for the eclipse to occur during the morning nighttime hours July 17. From South America, the moon is already in eclipse as it rises around sunset July 16; and in Australia, the moon is in eclipse as it sets around sunrise July 17. The worldwide map below shows more specifically where the eclipse is visible.
Read more: Partial lunar eclipse on July 16-17
Why does a full moon look full? Remember that half the moon is always illuminated by the sun. That lighted half is the moon’s day side. In order to appear full to us on Earth, we have to see the entire day side of the moon. That happens only when the moon is opposite the sun in our sky. So a full moon looks full because it’s opposite the sun.
That’s also why every full moon rises in the east around sunset – climbs highest up for the night midway between sunset and sunrise (around midnight) – and sets around sunrise. Stand outside tonight around sunset and look for the moon. Sun going down while the moon is coming up? That’s a full moon, or close to one.
Just be aware that the moon will look full for at least a couple of night around the instant of full moon.
Often, you’ll find two different dates on calendars for the date of full moon. That’s because some calendars list moon phases in Coordinated Universal Time, also called Universal Time Coordinated (UTC). And other calendars list moon phases in local time, a clock time of a specific place, usually the place that made and distributed the calendars. Translate UTC to your local time.
Want to know the instant of full moon in your part of the world, as well as the moonrise and moonset times? Visit the Sunrise Sunset Calendars site, remembering to check the moon phases plus moonrise and moonset boxes.
If a full moon is opposite the sun, why doesn’t Earth’s shadow fall on the moon at every full moon? The reason is that the moon’s orbit is titled by 5.1 degrees with respect to Earth’s orbit around the sun. At every full moon, Earth’s shadow sweeps near the moon. But, in most months, there’s no eclipse.
As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.
Bottom line: Full moon – when the moon is most opposite the sun for this month – falls on July 16, 2019, at 21:38 UTC. Translate UTC to your time zone. This full moon will undergo a partial lunar eclipse.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.