COLORADO SPRINGS (KXRM/KSTU) — You can expect two full moons to rise in the sky in October. You’ll see the Harvest Moon on Thursday, followed by the rare Blue Moon on Halloween.

The Harvest Moon usually appears in September and bears its name because it occurs closest to the autumnal equinox. The Sept. 2 full moon occurred too early to be known as the harvest moon.

“The harvest moon is the nearest full moon in date to the autumnal equinox. What that is, in the past long ago, the Native Americans used the moon, but they called it the Harvest Moon, to know when to harvest their crops,” Space Foundation Discovery Center’s Space Education Specialist Jeff Gonyea said.

The Harvest Moon is set to appear full to the naked eye for about three days.  

“On Sept. 30 and Oct. 2, more than 99% of the moon will be illuminated, so it’s almost like getting three days of a full moon,” said Gonyea. “The Native Americans labeled it the Harvest Moon because, with that extra light, they worked late into the night so that light from the full moon helped them work longer on those days to gather in their harvest.”

The Blue Moon, which will occur Oct. 31, will be the second full moon in the same calendar month — which is the reason behind its name.

“Is it going to be a blue moon up in the sky? Sorry, everybody, no,” Gonyea said.

According to Gonya, there is a seasonal Blue Moon and there is a monthly Blue Moon. 

“In olden times, they referred to the Blue Moon as the third full moon out of four in a season, so this autumn, September, October, and November is the autumn season,” he said. “September, we had a full moon. October, we’re getting two full moons, and then there’ll be a full moon in November. So that second one in October was referred to as the Blue Moon as well in olden times. We will get another one of those in August of the next year 2021.” 

According to the Farmers’ Almanac, the last time a full moon happened on Halloween night in all U.S. time zones was in 1944.

“The phrase ‘once in a blue moon’ actually denotes a long period of time,” Gonyea said.

To learn more about the night sky and space, the Space Foundation Discovery Center will be restarting its Virtual Family Star Party on Tuesday.

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