December 1991 lunar eclipse
A partial lunar eclipse occurred at the Moon’s descending node of orbit on Saturday, December 21, 1991, with an umbral magnitude of 0.0876. 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 only about 23 hours before perigee, the Moon's apparent diameter was larger.
This eclipse was the last of four lunar eclipses in 1991, with the others occurring on January 30, June 27, and July 26.
Visibility
The eclipse was completely visible over northeast Asia, much of North America, and much of the Pacific Ocean, seen rising over central, south, and east Asia, and Australia and setting over South America and northern Europe.Eclipse details
Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.| Parameter | Value |
| Penumbral Magnitude | 1.06511 |
| Umbral Magnitude | 0.08762 |
| Gamma | 0.97094 |
| Sun Right Ascension | 17h55m52.1s |
| Sun Declination | -23°26'13.9" |
| Sun Semi-Diameter | 16'15.5" |
| Sun Equatorial Horizontal Parallax | 08.9" |
| Moon Right Ascension | 05h56m15.5s |
| Moon Declination | +24°25'15.3" |
| Moon Semi-Diameter | 16'38.0" |
| Moon Equatorial Horizontal Parallax | 1°01'02.6" |
| ΔT | 58.3 s |
Eclipse season
This eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months 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.| December 21 Descending node | January 4 Ascending node |
| Partial lunar eclipse Lunar Saros 115 | Annular solar eclipse Solar Saros 141 |
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 March 3, 1988
- Followed by: Lunar eclipse of October 8, 1995
Tzolkinex
- Preceded by: Lunar eclipse of November 8, 1984
- Followed by: Lunar eclipse of January 31, 1999
Half-Saros
- Preceded by: Solar eclipse of December 15, 1982
- Followed by: Solar eclipse of December 25, 2000
Tritos
- Preceded by: Lunar eclipse of January 20, 1981
- Followed by: Lunar eclipse of November 20, 2002
Lunar Saros 115
- Preceded by: Lunar eclipse of December 10, 1973
- Followed by: Lunar eclipse of December 31, 2009
Inex
- Preceded by: Lunar eclipse of January 9, 1963
- Followed by: Lunar eclipse of November 30, 2020
Triad
- Preceded by: Lunar eclipse of February 19, 1905
- Followed by: Lunar eclipse of October 21, 2078
Half-Saros cycle
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days. This lunar eclipse is related to two partial solar eclipses of Solar Saros 122.| December 15, 1982 | December 25, 2000 |