| Type: | penumbral |
| Date: | August 6, 2009 |
| Gamma: | 1.3572 |
| Magnitude: | −0.6642 |
| Saros Ser: | 148 |
| Saros No: | 3 of 71 |
| Penumbral: | 189 minutes, 47 seconds |
| P1: | 23:04:21 |
| Greatest: | 0:39:11 |
| P4: | 2:14:08 |
| Previous: | July 2009 |
| Next: | December 2009 |
A penumbral lunar eclipse occurred at the Moon’s ascending node of orbit on Thursday, August 6, 2009,[1] with an umbral magnitude of −0.6642. 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 2.1 days after apogee (on August 3, 2009, at 22:40 UTC), the Moon's apparent diameter was smaller.[2]
This eclipse was the third of four lunar eclipses in 2009, with the others occurring on February 9 (penumbral), July 7 (penumbral), and December 31 (partial).
The eclipse was completely visible over South America, Africa, and Europe, seen rising over much of North America and setting over central and south Asia.[3]
Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.[4]
| Penumbral Magnitude | 0.40379 | |
| Umbral Magnitude | −0.66417 | |
| Gamma | 1.35724 | |
| Sun Right Ascension | 09h04m42.0s | |
| Sun Declination | +16°42'38.9" | |
| Sun Semi-Diameter | 15'46.1" | |
| Sun Equatorial Horizontal Parallax | 08.7" | |
| Moon Right Ascension | 21h02m46.3s | |
| Moon Declination | -15°34'32.9" | |
| Moon Semi-Diameter | 14'45.9" | |
| Moon Equatorial Horizontal Parallax | 0°54'11.4" | |
| ΔT | 66.0 s |
See also: Eclipse cycle. 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.[5] [6] [7]
The lunar year series repeats after 12 lunations or 354 days (Shifting back about 10 days in sequential years). Because of the date shift, the Earth's shadow will be about 11 degrees west in sequential events.
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 partial solar eclipses of Solar Saros 155.