The next full moon will form a lunar trio that will be visible from San Diego this week.

When September’s full moon rises at 7:34 p.m. on Tuesday, it will not only be a supermoon, but also this year’s harvest moon, coinciding with a partial lunar eclipse.

Here’s what makes this month’s Super Harvest Moon partial lunar eclipse so special.

What is a supermoon?

A supermoon occurs when a full phase of the moon coincides with a particularly close orbit around the Earth. This usually only happens three or four times a year, and in a row, because the moon’s oval orbit is constantly changing.

A supermoon is obviously not larger, but it can appear that way.

This supermoon will be about 357,000 kilometers from Earth. The next one will appear in October.

What is a harvest moon?

There is a Harvest Moon once a year, usually in September or October, depending on which full moon is closest to the autumn equinox. This year the autumn equinox is on September 22nd.

The name comes from a time before electricity, when, according to NASA, farmers relied on the light of the moon to harvest their crops late into the night before winter set in. The light of the full moon was especially important to farmers in the fall, as this was when they were able to harvest the most crops.

Each month’s full moon may also have Native American names associated with the crops harvested under that month’s moon. The moon in September is also known as the Corn Moon. Europeans may call the moon the Fruit Moon or the Barley Moon.

What is a lunar eclipse?

A partial lunar eclipse is also expected to be seen by people in North America, South America, Africa and Europe. A partial lunar eclipse occurs when the Earth passes between the Moon and the Sun, casting a shadow on the Moon.

Will the lunar eclipse be visible in San Diego?

Only a tiny portion of the Moon will be obscured by this eclipse. At the peak of the eclipse, it will only look as if the Moon has been cut out of its northwest corner by a tiny bit.

The moon is close to the horizon, so if you want to observe the lunar eclipse you will need a clear view to the east.

Visibility also depends on weather conditions. Get your First Alert forecast here.

When is the supermoon eclipse?

The penumbral eclipse – when the moon is in the Earth’s outer shadow – begins in San Diego at about 5:41 p.m. During this phase, the moon only gets slightly darker.

Earth’s umbra, or inner shadow, will begin to obscure the Moon around 7:12 p.m.

The maximum solar eclipse, which will only reach a magnitude of 0.085 of 1 in San Diego, is expected to occur at 7:44 p.m.

The entire solar eclipse will last nearly three hours and end at 9:47 p.m.

Do I need to wear safety glasses?

Unlike solar eclipses, observing a lunar eclipse does not require protective glasses and can be safely viewed with the naked eye, NBC News reports.

When is the next lunar eclipse?

Another lunar eclipse will not be visible from North America until March 13, 2025. On that day, San Diego can experience a total lunar eclipse.