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January 1991 lunar eclipse
A penumbral lunar eclipse occurred at the Moon’s descending node of orbit on Wednesday, January 30, 1991,[1] with an umbral magnitude of −0.1106. 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 about 1.9 days after perigee (on January 28, 1991, at 8:35 UTC), the Moon's apparent diameter was larger.[2] This eclipse was the first of four lunar eclipses in 1991, with the others occurring on June 27 (penumbral), July 26 (penumbral), and December 21 (partial). VisibilityThe eclipse was completely visible over North and South America, seen rising over northeast Asia and the central Pacific Ocean and setting over much of Africa and Europe.[3]
Eclipse detailsShown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.[4]
Eclipse seasonThis 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.
Related eclipsesEclipses in 1991
Metonic
Tzolkinex
Half-Saros
Tritos
Lunar Saros 143
Inex
Triad
Lunar eclipses of 1988–1991This 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 lunar eclipses on June 27, 1991 (penumbral) and December 21, 1991 (partial) occur in the next lunar year eclipse set.
Saros 143This eclipse is a part of Saros series 143, repeating every 18 years, 11 days, and containing 72 events. The series started with a penumbral lunar eclipse on August 18, 1720. It contains partial eclipses from March 14, 2063 through June 21, 2225; total eclipses from July 2, 2243 through April 13, 2712; and a second set of partial eclipses from April 25, 2730 through July 9, 2856. The series ends at member 72 as a penumbral eclipse on October 5, 3000. The longest duration of totality will be produced by member 36 at 99 minutes, 9 seconds on September 6, 2351. All eclipses in this series occur at the Moon’s descending 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.
Tritos seriesThis 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.
Half-Saros cycleA 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 partial solar eclipses of Solar Saros 150.
See alsoNotes
External links
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