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Year's Farthest Full Moon Also A Blue Moon!

The Full Moon falling on May 20, at 2:11 a.m. Universal Time (May 19, 10:11 p.m. Eastern Daylight Time) will be the farthest, smallest Full Moon to light up the sky in 2008. In the course of one month, the Moon's distance from the Earth varies by about 30,000 miles. When the Moon comes closest to Earth for the month, the Moon is said to be at perigee. When the Moon reaches its most distant point for the month, the Moon is at apogee. In 2008, the Full Moon most closely aligns with apogee in May.
The month as measured by sucessive returns to Full Moon (the lunar or synodic month) is nearly two days longer than the month as measured by sucessive returns to apogee (the anomalistic month). The Full Moon in the calendar months ahead will not realign with apogee. Each month, the Full Moon will come a bit closer to Earth and will appear a bit larger in our sky. On December 12, 2008, we'll have the closest and largest Full Moon of the year!

Realignment of Full Moon & Apogee

Successive returns to Full Moon (or New Moon) represent a mean period of 29.53059 days. On the other hand, successive returns to apogee (or perigee) happen in mean periods of 27.55455 days. Amazingly, however, 14 lunar months almost exactly equal 15 anomalistic months:
14 x 29.53059 days = 413.428 days
15 x 27.55455 days = 413.318 days
This time period is pretty much equal to 1 year 1 month and 18 days. Hence, the next smallest, closest Full Moon will fall on July 7, 2009.

Alignment of Full Moon with Perigee

There's another way to look at this cycle:
7 lunar months = 7.5 anomalistic months
What this means is 7 lunar months after the Full Moon aligns with apogee this May 20, the Full moon will align with perigee on December 12, 2008. Keeping in mind that the Full Moon will realign with perigee some 1 year 1 month and 18 days thereafter, that places the date of the following Full Moon/Perigee on January 30, 2010.

May 2008 Full Moon Also An "Old-Style" Blue Moon

More often than not, only three Full Moons occur in one season - a season being the period between a solstice and an equinox, or vice versa. Occasionally, however, four Full Moons do fall in one season, and the third of these four Full Moons is sometimes dubbed a blue moon - or what I like to call an "old-style" blue moon. I refer to the much more popular definition of the term - the second of two Full Moons to occur in one calendar month - as a "new-style" blue moon. Anyway, the May 2008 Full Moon is the third of four Full Moons to fall between the March 2008 equinox and the June 2008 solstice.

Blue Moon Cycles

Blue moons also have cycles. 235 lunar months pretty much equal 19 calendar years. Sure enough, 19 years later - on May 20, 2027 - the May Full Moon is the third of four Full Moons falling between the March equinox and September equinox! Keep in mind that there are only 228 calendar months in these 19 years (19 x 12 = 228), but 235 Full Moons. With 76 seasons in this 19-year period (19 years x 4 seasons/year = 76 seasons), it's inevitable that 7 of these 76 seasons (76 seasons x 3 months/season = 228 months) have to harbor 4 Full Moons!

copyright 2008 by Bruce McClure

Apogee/Perigee & New/Full Moon Calculator

Phases of the Moon: 2001 to 2100

Equinox & Solstice Dates

April 2008 Feature * June 2008 Feature