A partial lunar eclipse occurred at the Moon’s ascending node of orbit on Sunday, June 4, 2012,[1] with an umbral magnitude of 0.3718. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A partial lunar eclipse occurs when one part of the Moon is in the Earth's umbra, while the other part is in the Earth's penumbra. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. Occurring about 1.1 days before perigee (on June 3, 2012, at 9:15 UTC), the Moon's apparent diameter was larger.[2]
The eclipse was completely visible over Australia, Antarctica, and the Pacific Ocean, seen rising over east Asia and setting over North and South America.[3]
Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.[4]
This eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a fortnight.
This eclipse is a member of a semester series. An eclipse in a semester series of lunar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.[5]
The penumbral lunar eclipses on February 9, 2009 and August 6, 2009 occur in the previous lunar year eclipse set, and the lunar eclipses on April 25, 2013 (partial) and October 18, 2013 (penumbral) occur in the next lunar year eclipse set.
This eclipse is a part of Saros series 140, repeating every 18 years, 11 days, and containing 77 events. The series started with a penumbral lunar eclipse on September 25, 1597. It contains partial eclipses from May 3, 1958 through July 17, 2084; total eclipses from July 30, 2102 through May 21, 2589; and a second set of partial eclipses from June 2, 2607 through August 7, 2715. The series ends at member 77 as a penumbral eclipse on January 6, 2968.
The longest duration of totality will be produced by member 38 at 98 minutes, 36 seconds on November 4, 2264. All eclipses in this series occur at the Moon’s ascending node of orbit.[6]
Eclipses are tabulated in three columns; every third eclipse in the same column is one exeligmos apart, so they all cast shadows over approximately the same parts of the Earth.
This eclipse is a part of a tritos cycle, repeating at alternating nodes every 135 synodic months (≈ 3986.63 days, or 11 years minus 1 month). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee), but groupings of 3 tritos cycles (≈ 33 years minus 3 months) come close (≈ 434.044 anomalistic months), so eclipses are similar in these groupings.
This eclipse is a part of the long period inex cycle, repeating at alternating nodes, every 358 synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee). However, groupings of 3 inex cycles (≈ 87 years minus 2 months) comes close (≈ 1,151.02 anomalistic months), so eclipses are similar in these groupings.
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (a half saros).[8] This lunar eclipse is related to two annular solar eclipses of Solar Saros 147.