New Years Eve 2009: Blue Moon

New Year’s Eve celebrations were a bit brighter this year with a blue moon shining in the sky Thursday night.

A blue moon — the second full moon in a month — isn’t really uncommon, occurring on average every 2 1/2 years. But “on New Year’s Eve it is very rare,” said Scott Kardel, a spokesman for the Palomar Observatory in San Diego County. The last one was in 1990.

The name is a bit misleading — the moon does not appear blue. Rather, the name refers to the expression “once in a blue moon.”

Though many stargazers probably watched the skies on New Year’s Eve, most astronomers don’t like full moons because they make the sky too bright, Kardel said.

“But a full moon is convenient if you’re out celebrating,” he said.

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