I would have liked to have gotten this entry in several weeks ago, since "Supermoon" was last night. However, I wanted to at least make a reference entry. Supermoon may roughly be only once a year, but full moon phases are roughly once a month; so there are frequent opportunities for observation or celebration. A "Supermoon" is to lunar phases, what Yule is to the eight seasonal Sabbats.
There are astronomical, stargazer, and lunar calendars each year if you check on Yahoo shopping or Amazon.com. The annual dates of the wheel of the year don't change, like the lunar dates. Supermoon is a great opportunity for a celebration or a stargazing night walk, but it won't happen again for 412 days.
From yesterdays San Francisco Chronicle:
Supermoon: The biggest and brightest full moon of the year arrives Saturday night. The event is a "supermoon," the closest full moon of the year. The moon will be about 221,802 miles from Earth, or about 15,300 miles closer than average. That proximity will make the moon appear about 14 percent bigger than it would if the moon were at its farthest distance, said Geoff Chester of the U.S. Naval Observatory in Washington.
A supermoon, is the coincidence of a full moon (or a new moon) with the closest approach the Moon makes to the Earth on its elliptical orbit, or perigee, leading to the technical name for a supermoon of the perigee-syzygy of the Earth-Moon-Sun system. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events such as earthquakes and volcanic eruptions. However, the evidence of such a link is widely held to be unconvincing.
Full moon is a lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent (ecliptic) longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.
Lunar eclipses can only occur at full moon, where the moon's orbit allows it to pass through the Earth's shadow. Lunar eclipses do not occur every month because the moon usually passes above or below the Earth's shadow (which is mostly restricted to the ecliptic plane). Lunar eclipses can occur only when the full moon occurs near the two nodes of the orbit, either the ascending or descending node. This causes eclipses to only occur about every 6 months, and often 2 weeks before or after a solar eclipse at new moon at the opposite node.
As seen from Earth, the hemisphere of the Moon that is facing the Earth (the near side) is almost fully illuminated by the Sun and appears round. Only during a full moon is the opposite hemisphere of the Moon, which is not visible from Earth (the far side), completely unilluminated.
The time interval between similar lunar phases—the synodic month—averages about 29.53 days. Therefore, in those lunar calendars in which each month begins on the new moon, the full moon falls on either the 14th or 15th of the lunar month. Because lunar months have a whole number of days, lunar months may be either 29 or 30 days long.
A lunar phase or phase of the moon is the appearance of the illuminated (sunlit) portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun. The half of the lunar surface facing the Sun is always sunlit, but the portion of this illuminated hemisphere that is visible to an observer on Earth can vary from about 100% (full moon) to 0% (new moon). The lunar terminator is the boundary between the illuminated and unilluminated hemispheres. Aside from some craters near the lunar poles such as Shoemaker, all parts of the Moon see around 14.77 days of sunlight followed by 14.77 days of "night" (there is no permanently "dark side" of the Moon).
A lunar phase or phase of the moon is the appearance of the illuminated (sunlit) portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun. The half of the lunar surface facing the Sun is always sunlit, but the portion of this illuminated hemisphere that is visible to an observer on Earth can vary from about 100% (full moon) to 0% (new moon). The lunar terminator is the boundary between the illuminated and unilluminated hemispheres. Aside from some craters near the lunar poles such as Shoemaker, all parts of the Moon see around 14.77 days of sunlight followed by 14.77 days of "night" (there is no permanently "dark side" of the Moon).
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