On the night of September 17, the Earth, Sun, and Moon will align, causing three celestial events to occur.

In many places, depending on the time zone, people can witness a harvest moon, a supermoon, and a lunar eclipse when the full moon rises.

Here’s what you need to know about these events:

Let’s start at the beginning: what is a full moon?

According to NASA, a full moon is defined as the moment when the moon is exactly 180 degrees opposite the sun. During this time, the sun almost completely illuminates the Earth’s satellite.

According to NASA, this month’s full moon will peak on Tuesday, September 17 at 10:35 p.m. EDT (or 2:35 a.m. GMT on Wednesday, September 18).

Full moons generally rise around sunset and set around sunrise. There are eight phases in the lunar cycle, which repeats every 29.5 days.

What is a partial lunar eclipse?

A partial lunar eclipse is a time when part of the full moon is covered by the Earth’s shadow.

The shadow expands and then retreats, but never reaches totality. In contrast, during a total lunar eclipse, the entire shadow of the Earth completely covers the moon.

The moon will begin moving into Earth’s partial shadow at 8:41 p.m. EDT Tuesday (12:41 a.m. GMT Wednesday). The initial eclipse may be subtle until the top of the moon begins to move into full shadow at 10:13 p.m. EDT Tuesday (2:13 a.m. GMT Wednesday).

The eclipse peaks at 10:44 p.m. EDT on Tuesday (2:44 a.m. GMT on Wednesday), with only the upper eight percent of the moon in full shadow.

The moon will exit full shadow at 11:16 p.m. EDT (03:16 GMT) and will exit partial shadow at 12:47 a.m. EDT, or 04:47 a.m. GMT on Wednesday morning.

What is a supermoon?

This moon will also be a supermoon.

A supermoon is defined as an astronomical phenomenon in which a full moon appears larger and brighter than normal. It occurs when the full moon occurs at the same time that its orbit is closest to the Earth.

According to NASA, the term “supermoon” was coined in 1979 by astrologer Richard Nolle to describe a full moon that occurs when the moon is “within 90 percent of its closest distance to Earth.”

Essentially, the Earth, the moon, and the sun are all in alignment at this point. At the other end of the lunar spectrum is the micromoon — when the full moon appears especially small and dim because it coincides with the point in the moon’s orbit where it is farthest from Earth.

Is this also a harvest moon?

The Harvest Moon is the full moon that falls closest to the autumnal equinox in the Northern Hemisphere. This year it occurs on September 22 at 12:43 GMT.

Yes, this is also a harvest moon.

According to the Farmer’s Almanac, “this full moon rises at about the same time – around sunset – for several evenings in a row.” This results in an abundance of bright moonlight early in the evening.

This phenomenon has traditionally helped farmers harvest their summer crops by giving them several extra evenings of moonlight, hence the name Harvest Moon.

The Harvest Moon has an orange and red hue. It appears larger and brighter than other full moons due to an optical illusion that occurs when a moon is close to the horizon.

The moon gets its color because moonlight is filtered by more particles in the Earth’s atmosphere than when the moonlight is high above us.

How will Tuesday’s event unfold?

• The full moon reaches its peak on Tuesday at 10:35 p.m. EDT (Wednesday at 2:35 a.m. GMT). At this time it also reaches its peak illumination.
• The eclipse will peak at 10:44 p.m. EDT (2:44 a.m. GMT).

The total duration of the partial lunar eclipse will be four hours and six minutes.

For observers in the United States Eastern Time Zone, the eclipse will be darkest on September 17 around 10:44 p.m. EDT.

In Europe and Africa, the eclipse will be visible in the early morning hours of September 18. In the UK, the eclipse will be most visible around 03:44 (BST) on September 18.

People living in the Gulf region will not be able to witness the peak of the eclipse, but they can see the moment when the partial eclipse begins at 5:15 a.m. local time on Wednesday.

The map below shows in which countries the solar eclipse will be largest on Tuesday.

How can you view the lunar eclipse and the harvest moon?

If you are in the right time zone, a casual stargazer can see the lunar eclipse, but it is better to be in a darker location.

NASA also recommends using binoculars “with a magnification of at least 7,” noting that “a magnification of 10 or 15 will produce more detail; you may need a tripod to steady the binoculars.”