DENVER (CBS4) – If you consider yourself a sky watcher then July 2015 may be special because the month features two full moons.

It has long been said when this happens the second of the two is called a Blue Moon.

But in reality it’s not one.

Barbara Kerns from Thornton sent in this photo of the "Beaver Moon" setting over  Longs Peak.

Barbara Kerns from Thornton sent in this photo of the “Beaver Moon” setting over Longs Peak in 2011.

“The reason that people think a Blue Moon is the second full moon of the month is because of a Sky & Telescope article from the 1940s that mistakenly described it that way,” said Jeff Tropeano with the Denver Astronomical Society.

In a 2004 Sky & Telescope article the magazine explains more about their Blue Moon blooper.

The real definition of a Blue Moon is quite different.

“When a season has four full moons in it, the third one is called a Blue Moon,” said Tropeano.

A season is defined as the time between a solstice and an equinox.

Tropeano says using the real definition of a Blue Moon the next one will occur on May 21, 2016.

For those who might be disappointed by this news, the American Heritage Dictionary does recognize both scenarios.

In addition to the above there are yet some other definitions of a Blue Moon that date back over 400 years, including one that created the phrase “once in a Blue Moon.”

Meteorologist Chris Spears writes about stories related to weather and climate in Colorado. Check out his bio or follow him on Twitter @ChrisCBS4.

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