A penumbral lunar eclipse occurred at the Moon’s ascending node of orbit on Friday, July 26, 1991, with an umbral magnitude of −0.8109. 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 2.25 days after apogee (on July 24, 1991, at 12:10 UTC), the Moon's apparent diameter was smaller.
This eclipse was the third of four lunar eclipses in 1991, with the others occurring on January 30 (penumbral), June 27 (penumbral), and December 21 (partial).
Visibility
The eclipse was completely visible over east Africa, much of Asia, Australia, and Antarctica, seen rising over much of Europe and west and central Africa and setting over northeast Asia and the central Pacific Ocean.
Eclipse details
Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.
Eclipse season
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.
Related eclipses
Eclipses in 1991
- An annular solar eclipse on January 15.
- A penumbral lunar eclipse on January 30.
- A penumbral lunar eclipse on June 27.
- A total solar eclipse on July 11.
- A penumbral lunar eclipse on July 26.
- A partial lunar eclipse on December 21.
Metonic
- Preceded by: Lunar eclipse of October 7, 1987
Tzolkinex
- Preceded by: Lunar eclipse of June 13, 1984
- Followed by: Lunar eclipse of September 6, 1998
Half-Saros
- Preceded by: Solar eclipse of July 20, 1982
- Followed by: Solar eclipse of July 31, 2000
Tritos
- Preceded by: Lunar eclipse of August 26, 1980
- Followed by: Lunar eclipse of June 24, 2002
Lunar Saros 148
- Preceded by: Lunar eclipse of July 15, 1973
- Followed by: Lunar eclipse of August 6, 2009
Inex
- Preceded by: Lunar eclipse of August 15, 1962
- Followed by: Lunar eclipse of July 5, 2020
Triad
- Preceded by: Lunar eclipse of September 24, 1904
Lunar eclipses of 1988–1991
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.
The lunar eclipses on June 27, 1991 (penumbral) and December 21, 1991 (partial) occur in the next lunar year eclipse set.
Saros 148
This eclipse is a part of Saros series 148, repeating every 18 years, 11 days, and containing 70 events. The series started with a penumbral lunar eclipse on July 15, 1973. It contains partial eclipses from October 10, 2117 through May 5, 2460; total eclipses from May 17, 2478 through September 14, 2676; and a second set of partial eclipses from September 25, 2694 through May 25, 3091. The series ends at member 70 as a penumbral eclipse on August 9, 3217.
The longest duration of totality will be produced by member 37 at 104 minutes, 29 seconds on July 10, 2568. All eclipses in this series occur at the Moon’s ascending node of orbit.
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 series
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.
Inex series
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.
Half-Saros cycle
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (a half saros). This lunar eclipse is related to two partial solar eclipses of Solar Saros 155.
See also
- List of lunar eclipses
- List of 20th-century lunar eclipses
Notes
External links
- 1991 Jul 26 chart Eclipse Predictions by Fred Espenak, NASA/GSFC
