December 1991 lunar eclipse
| Partial eclipse | |||||||||||||
The Moon's hourly motion shown right to left | |||||||||||||
| Date | December 21, 1991 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Gamma | 0.9709 | ||||||||||||
| Magnitude | 0.0876 | ||||||||||||
| Saros cycle | 115 (56 of 72) | ||||||||||||
| Partiality | 64 minutes, 4 seconds | ||||||||||||
| Penumbral | 251 minutes, 29 seconds | ||||||||||||
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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 (on December 22, 1991, at 9:25 UTC), 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 (penumbral), June 27 (penumbral), and July 26 (penumbral).