Whatever its color, rare ‘blue moon’ catches the gaze of astronomy buffs
Astronomy buffs in Taiwan yesterday observed a rare “blue moon,” which refers to the appearance of a second full moon in a calendar month and a saying that dates back to the American Farmers’ Almanac, rather than referring to the color, the Taipei Astronomical Museum said.
Just don’t expect it to be “blue,” museum researcher Chang Kueilan had said, noting that it would look like any other full moon.
The moonrise, which took place at 6:23 p.m., was the second full moon in July, following the first one on July 2, the museum said.
The moon was clearly visible by looking up to the lower eastern sky anytime after 6:30 p.m., said Chang.
According to Chang, the modern usage of “blue moon” can be attributed to a Sky & Telescope Magazine misinterpretation.
In an article published by the astronomy magazine in 1946, it mistakenly defined a blue moon as the second full moon in a calendar month, which is how it is understood today, Chang said.
The magazine said that 12 full moons are usually perceivable each year, one in each calendar month, but that because a lunar month averages about 29.53 days, the extra days accumulated throughout the year eventually result in 13 full moons in a year.
The magazine definition was a misinterpretation of the Maine Farmers’ Almanac, which began listing the dates of forthcoming blue moons in 1819 and was the origin of the phrase “once in a blue moon.”
The almanac had defined a blue moon as the third full moon in a three-month season that has four moons rather than the usual three, Chang said.
Under this old formula, the next blue moon will come in 2016.
“Regardless of its origin, a blue moon is worth watching because of its unique timing,” she said, adding that the celestial event last occurred in August 2012 and will not occur again until January 2018.
A rare “blue moon” is seen yesterday evening in the sky above Taipei.