The last time a Supermoon and an eclipse coincided, Ronald Reagan was half-way through his first time as President of the United States and moviegoers were anxiously awaiting the third installment of the Star Wars movies, “Return of the Jedi”. The next time it happens, after September 27/28 of this year, will be 2033

A Supermoon occurs when the moon appears to be larger, because it is closer to the Earth. Our elliptical, or egg shaped, orbit causes the distance between the Earth and the Moon to vary. At its furthest point from the Earth or “apogee” it is 252,000 miles away, while at its “perigee” or closest point, it is only 226,000 miles away. A Supermoon occurs at or very near the perigee.

This particular supermoon will coincide with a lunar eclipse, which occurs when the Moon passes through the shadow of the Earth as cast by the Sun.

“During a lunar eclipse, the Moon passes into the Earth’s shadow. But it doesn’t completely go dark.That’s because the Sun’s light is refracted and scattered forward through our atmosphere and onto the Moon’s surface. Red light scatters least, so the Moon often takes on a striking dull red or copper color during a total lunar eclipse,” according to a statement from the Slooh Community Observatory.

The event, known as a “Blood Supermoon” is expected to occur on the evening of September 27/28 and will reach it’s strongest point at 10:47 pm EST. Weather permitting it will be visible in its entirity in eastern and central North America, western Europe and all of South America. On the west coast of North America moonrise will occur during the eclipse.

The eclipse later this month will be the fourth, and most spectacular, of a tetrad or a series of four eclipses in two years. The first two of these were on April 15 and October, 8 2014, the third was on April 4 of this year. The September eclipse is expected to last 72 minutes, 67 more than the April eclipse and is the moon will appear to be 13 percent larger.

For those who can’t observe the eclipse because of location or weather, the Slooh observatory will have complete online coverage at Slooh.com.

Additional information about the event is available in this video from NASA’s Goddard Space Flight Center.