A rare Friday the 13th harvest moon has been thrilling skywatchers.

The full moon is the first to occur on Friday the 13th for almost 20 years and that kind of timing won't recur for 30 years.

According to Old Farmer’s Almanac, the harvest moon is the full moon closest to the beginning of fall or the autumnal equinox.

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The last time a full moon occurred on Friday the 13th was on Oct. 13, 2000, said the almanac. The annual periodical notes that the rare event will not occur again until Aug. 13, 2049.

The rare event sparked plenty of "spooky" chatter on social media.

The harvest moon is named after the harvest season with which it coincides.

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“Farmers can work late into the night by the light of this moon,” explained NASA in a blog post. “The harvest moon is an old European name for this full moon; the Oxford English Dictionary cites the year 1706 for the first published use of the name."

NASA also noted that this particular moon is important to many cultures. "Many cultures have holidays connected to this moon, including the mid-autumn festival in some East Asian countries and Chuseok in Korea."

The harvest moon will reach its peak on Sept. 14 at 12.33 a.m. EDT, says the Old Farmer’s Almanac.

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