A penumbral lunar eclipse occurred at the Moon’s ascending node of orbit on Saturday, May 25, 2013,[1] with an umbral magnitude of −0.9322. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A penumbral lunar eclipse occurs when part or all of the Moon's near side passes into 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 only about 18 hours before perigee (on May 25, 2013, at 21:40 UTC), the Moon's apparent diameter was larger.[2]
This eclipse was visually imperceptible due to the small entry into the penumbral shadow. It also marked the beginning of Saros series 150.
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. The first and last eclipse in this sequence is separated by one synodic month.
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]
This eclipse is a part of Saros series 150, repeating every 18 years, 11 days, and containing 71 events. The series started with a penumbral lunar eclipse on May 25, 2013. It contains partial eclipses from August 20, 2157 through April 19, 2554; total eclipses from April 29, 2572 through August 28, 2770; and a second set of partial eclipses from September 7, 2788 through February 8, 3041. The series ends at member 71 as a penumbral eclipse on June 30, 3275.
The longest duration of totality will be produced by member 36 at 105 minutes, 16 seconds on July 4, 2680. All eclipses in this series occur at the Moon’s ascending node of orbit.[6]
Greatest
First
The greatest eclipse of the series will occur on 2680 Jul 04, lasting 105 minutes, 16 seconds.[7]
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.
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