A partial lunar eclipse occurred at the Moon’s ascending node of orbit on Tuesday, June 4, 1974,[1] with an umbral magnitude of 0.8270. 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 4.5 days before apogee (on June 9, 1974, at 10:35 UTC), the Moon's apparent diameter was smaller.[2]
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]
This eclipse is a part of Saros series 120, repeating every 18 years, 11 days, and containing 83 events. The series started with a penumbral lunar eclipse on October 16, 1000. It contains partial eclipses from May 31, 1379 through August 4, 1487; total eclipses from August 14, 1505 through May 14, 1938; and a second set of partial eclipses from May 24, 1956 through July 28, 2064. The series ends at member 83 as a penumbral eclipse on April 7, 2479.
The longest duration of totality was produced by member 43 at 104 minutes, 55 seconds on January 24, 1758. All eclipses in this series occur at the Moon’s ascending node of orbit.[6]
Greatest
First
The greatest eclipse of the series occurred on 1758 Jan 24, lasting 104 minutes, 55 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.
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 total solar eclipses of Solar Saros 127.
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