Friday, 7 September 2012

BLUE MOON

A blue moon is the appearance of the third full moon in a season that has four full moons, instead of the usual three. It is never visually blue. Because a blue moon occurs only every two or three years, the term blue moon is used colloquially to mean a rare event, as in the phrase "once in a blue moon".

One lunation (an average lunar cycle) is 29.53 days. There are 365.26 days in a solar year. Therefore, about 12.37 lunations (365.26 days divided by 29.53 days) occur in a solar year. In the widely used Gregorian calendar, there are 12 months (the word month is derived from moon) in a year. Each calendar year contains roughly 11 days more than the number of days in 12 lunar cycles. The extra days accumulate, so every two or three years (7 times in the 19-year Metonic cycle), there is an extra full moon. The extra moon necessarily falls in one of the four seasons, giving that season four full moons instead of the usual three, and, hence, a blue moon.

This is a photo of the blue moon I took in Fremantle last week. The gull is incidental!

This post is part of the Skywatch Friday meme,

and also part of the Weekly TopShot meme.


11 comments:

  1. I love this shot with the bird and the moon. It is a beautiful moon. Happy SKywatching!

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  2. What a terrific shot. On the day of the recent blue moon, the blue moon appeared at 8:58 a.m., way too late in the morning to be visible on a normal day this time of year, plus our skies were dense with cloud cover so I didn't even see it!

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  3. Very cool shot and great find!

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  4. That is such an impressive shot... Well done !

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  5. I don't know I think the gull is an integral part of the photo. Boom & Gary of the Vermilon River, Canada.

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  6. Ha! We know better. These things don't just happen by accident!

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  7. What a wonderful shot, the gull in the foreground really adds so much to the story of your image... Thanks for sharing on Weekly Top Shot #47!

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  8. What a great capture for the full moon.

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