On Friday the 13th, a complete "harvest moon" will be visible in the night sky

A "lunar harvest" will be visible in the night sky this Friday the 13th and the next day, and although the timing seems a bit worrisome, there is no reason to be scared by this sky-watching event.

This full moon is a so-called mini-moon because it occurs when the moon is at its furthest point in its elliptical orbit around the Earth, at some 252,000 km of astronomers called the lunar apogee. When the opposite occurs – when the moon fills at its closest point to the Earth, called lunar perigee – it becomes a super moon.

Although mini-moons – also called micromoons – seem smaller and lighter than moons at other times in the lunar cycle, the differences are usually too subtle to be noticed at the naked eye. "It will look a little smaller and about 13% lower than average, but it's not a huge effect," said Patrick Hartigan, an astrophysicist at Rice University in Houston.

In the Northern Hemisphere, the September full moon is traditionally called the harvest moon, as it occurs almost at the peak of the fall harvest season. "There are several nights in a row where, just after sunset, the moon will hang near the horizon," Hartigan said. "That's why people used it as natural light to help them harvest."