Two full moons occur during the month of August 2012. Although, technically this second full moon does not fit the definition of a “Blue Moon” that was coined by the "Maine Farmer’s Almanac" in 1937, it is still rare (occurring once every several years). The “Blue Moon” coined in the Maine Farmer’s almanac, as an agrarian phenomena, only occurs when a season contains four full moons. The misnomer given to the second full moon (like the one this month) occurring during a single month stems from an astronomer’s misinterpretation of the aforementioned almanac’s definition.
During 1946 "Once in a Blue Moon" (an article written by James Hugh Pruett in "Sky&Telescope") claimed that the second full moon in a month was actually a “Blue Moon”. This definition took hold in popular culture hence many view the second full moon occurring on August 31, 2012 as a “Blue Moon”. If you are a diehard almanac follower, however, do not worry, as you will only have to wait a year for the next seasonal “Blue Moon”, which will rise on August 21, 2013.
The term Blue Moon has a rich history tracing back to the mid 1500’s. The first literary work referencing a blue moon was a poem printed by John Schott (“English Observant Franciscan Friars”) in Strasburg in 1528. This poem written by William Roy and Jerome Barlow was entitled "Rede me and be nott wrothe, for I saye no thinge but trothe". However, the meaning of "Blue Moon" held a very different meaning in this poem than it does in our current vernacular.
It was quite a dissident piece of literary work speaking out overtly against the “blue bloods” or nobility and the papal hierarchy of the time. The reference to the blue moon I am citing is on page 114. The exact excerpt in old English read,
“Yf they faye the mone is belewe/ We muft beleve that it is true/"
Another type of “Blue Moon” is actually a blue tinge or hue to the moon caused by particulate matter in the atmosphere. This type of “Blue Moon” phenomena is very rare and actually matches its name literally rather than metaphorically. Typically, it requires very small silt like particles that absorb, disperse, or reflect orange/red wavelengths (590-750nm) from the visible light spectrum radiated by the moon while allowing the blue/green wavelengths (450nm-570nm) in the visible spectrum to pass through.
Although, there is no real astrological significance to the second full moon this month if you enjoy the light of a good full moon you have two opportunities to view one this month. And, whether you subscribe to the folklore version of a Blue Moon’s definition (based on the Gregorian calendar) or prefer the more technical almanac version (based on the seasonal calendar) the second full moon this month definitely provides quite a conversation piece for the dinner table. The Blue moon with its rich history, in our vernacular, is sure to put on quite a show for us. Therefore, if you enjoy the night sky or just want see what the hubbub is about take a peek at the second full moon this month on August 31st.
Reference: Rede me and be nott wrothe, for I saye no thinge but trothe : printed by John Schott at Strasburg in 1528 by Roy, William, fl. 1527-1531. Published 1871 pg 114