Step outside on Sunday night and you’ll get a rare astronomical treat: A so-called “supermoon” undergoing a total lunar eclipse.

To understand what that is, you need to first set aside what you learned in elementary school about moons and planets from classroom models — and disregard all of those beautiful drawings and graphics you’ve seen since then.

The truth is hardly any moon or planet follows a perfectly circular path.

Our moon’s orbit is more of a bowed, oblong pattern around Earth. That means there’s a point in which it is closer to Earth and, thus, looks a little bigger.

That’s called a supermoon.

According to NASA, the moon appears 14 percent larger than it usually does when it’s a supermoon.

It’ll still be about 220,000 miles away from Earth. But that’s 31,000 miles closer than the outskirts of its orbit.

Combine that with a total lunar eclipse — an event in which the moon passes behind the Earth into its shadow, giving it a red tint — and you have what’s called a supermoon lunar eclipse.

We’ve had those two phenomena come together only five times since 1900 — in 1910, 1928, 1946, 1964 and 1982, NASA said in an animated video on its website, which can be found at http://​svs.gsfc.nasa.gov/​cgi-bin/​details.cgi?aid=11981.

On Sunday, for the first time in 33 years, it’ll happen again.

If you don’t see Sunday’s Supermoon Lunar Eclipse, the next one will be in 2033.

To help drum up some excitement, the University of Toledo is hosting a free special viewing party at its Ritter Auditorium, weather permitting.

The event is from 9 to 11:30 p.m., with prime viewing from 10 to 11 p.m., according to the planetarium’s director, Michael Cushing, UT associate professor of astronomy.

The plan is to have several telescopes on the lawn outside the planetarium, which is on the main campus near West Bancroft Street. Visitors are allowed to come and go. The planetarium will have a large telescope available. It also will present a 10-minute video running continuously from 9 p.m. to 11:30 p.m., and have staff available to answer questions, he said.

The moon will be at its reddest about 10:45 p.m., Mr. Cushing said.

The red tint is the result of blue rays from the sun being removed by Earth’s atmosphere.

Red rays pass through, he said.

“As the moon passes into the shadow of the Earth, red light from the sun is filtered and bent, or refracted, through the Earth’s atmosphere and onto the moon’s surface,” Mr. Cushing said.

Also, the Toledo Astronomical Association will host a public viewing of the supermoon lunar eclipse starting at 9 p.m. at Olander Park.

The moon, according to NASA, does not make its own light. It reflects light it receives from the sun.

Lunar eclipses, unlike solar eclipses, are slow-moving events, Mr. Cushing said.

Sunday’s eclipse is expected to begin about 9:07 p.m. and continue until 12:27 a.m., with the moon being completely eclipsed from about 10:11 p.m. to 11:23 p.m., he said.

Don’t fret if you can’t make it to UT.

You should be able to see the supermoon lunar eclipse from just about anywhere, provided you have a clear line of sight to the south.

Contact Tom Henry at: thenry@theblade.com, 419-724-6079, or via Twitter @ecowriterohio.

First Published September 26, 2015, 4:00 a.m.