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Full Moon Makes an Encore Appearance in July Skies

Posted on: Tuesday, 27 July 2004, 06:00 CDT

Don't say "once in a blue moon" just yet. A blue moon will show up this weekend -- well, depending on your definition.

A "blue moon" is commonly known as two full moons in a calendar month. There was a full moon July 2, and on Saturday there will be a second full moon, or the blue moon, in North America. In every 19- year span, a blue moon appears only seven times. In 1999, there were two blue moons; a pair of full moons in January and in March.

However, that is a "modern definition" of a blue moon, said Robert Bigelow, education program specialist at the Hansen Clark Planetarium in Salt Lake City. Quoting from Sky and Telescope, Bigelow said the modern definition is a misinterpretation of a 1937 article on the blue moon.

The original definition of a blue moon comes from Maine Farmers' Almanacin 1937: each season normally has three full moons, and farmers adopted the Algonquian Indian custom of giving each moon a name to keep track of the four seasons. For example, in the fall, the first moon is called the "harvest moon," the second is the "hunter moon" and the third is the "beaver moon."

However, sometimes a fourth moon shows up during a season. In order to keep the moon names in order, the third moon would be the blue moon, said Bigelow. If there was an extra moon in fall season, for example, the order would go like this: harvest moon, hunter moon, blue moon, then beaver moon.

"By that definition, we won't actually have a blue moon this year," said Bigelow. (This Saturday's full moon is the second of the summer season, with the third and last one coming in late August.) The next blue moon by the Maine Farmers' Almanac definition will occur Aug. 19, 2005.

Still, the modern definition is what most people go by. It made it into the game Trivial Pursuit and was published in the The Kids' World Almanac of Records and Facts, Bigelow said.

The contrasting definitions reminds him about the debate over the start of the new millennium. By definition it was 2001, however most celebrated the new millennium in 2000.

Just like the millennium celebrations, "why not do a celebration for both [blue moons]?" Bigelow asked. The next "modern" blue moon won't occur until June 2007.

"If we celebrate both, we have more parties," Bigelow said.

One of those parties celebrating the blue moon on Saturday will be in the desert community of Kayenta, seven miles outside of St. George. The Blue Moon Festival is an arts festival as well as a fund- raiser for the community Desert Rose Labyrinth and sculpture garden.

Historically, labyrinths are places for meditation, said Cheryl Collins, organizer of the Blue Moon Festival. There are three labyrinths in Utah, the largest in Kayenta.

"We thought it would be perfect to walk to labyrinths when a full moon is out," Collins said.

Collins said she didn't know about the old definition of a blue moon, but would consider having another Blue Moon Festival next August.

The relative rarity of a blue moon, by either definition, explains the phrase "once in a blue moon," or another way of saying " seldom." The extra moon also explains why the No. 13 is considered unlucky because the extra moon disrupted the 12-full-moon cycle, Bigelow said.

jdoria@sltrib.com

Blue Moon:

Modern definition: Two full moons in a calendar month.

Old definition: An extra full moon in a season, which usually has three. When there are four full moons in a season, the third gets called the "blue moon." For example, in such a fall season, the order would go like this: harvest moon, hunter moon, blue moon, then beaver moon.

Last "modern" blue moon: Two blue moons showed up in 1999: there were a pair of full moons in January and a pair in March.

The next blue moon: Saturday, July 31, under the modern definition. The first full moon of the month was July 2. For the old definition, the next blue moon will show up Aug. 19, 2005. For the modern definition, the next blue moon after Saturday will be in June 2007.

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