| Penumbral eclipse | |||||||||
 The Moon's hourly motion shown right to left | |||||||||
| Date | September 27, 1977 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Gamma | 1.0768 | ||||||||
| Magnitude | −0.1361 | ||||||||
| Saros cycle | 117 (50 of 72) | ||||||||
| Penumbral | 257 minutes, 30 seconds | ||||||||
| |||||||||
A penumbrallunar eclipse occurred at the Moon’sdescending node of orbit on Tuesday, September 27, 1977,[1] with an umbralmagnitude of −0.1361. A lunar eclipse occurs when theMoon moves into theEarth'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 asolar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on thenight side of Earth. Occurring about 6.25 days beforeapogee (on October 3, 1977, at 14:45 UTC), the Moon's apparent diameter was smaller.[2]
The eclipse was completely visible overNorth America, northwesternSouth America, and the central and easternPacific Ocean, seen rising overeast andnortheast Asia andAustralia and setting over much ofSouth America and theAtlantic Ocean.[3]
 |
Shown below is a table displaying details about this particular lunar eclipse. It describes various parameters pertaining to this eclipse.[4]
| Parameter | Value |
|---|---|
| Penumbral Magnitude | 0.90076 |
| Umbral Magnitude | −0.13605 |
| Gamma | 1.07682 |
| Sun Right Ascension | 12h15m08.1s |
| Sun Declination | -01°38'19.9" |
| Sun Semi-Diameter | 15'57.6" |
| Sun Equatorial Horizontal Parallax | 08.8" |
| Moon Right Ascension | 00h13m53.7s |
| Moon Declination | +02°36'15.1" |
| Moon Semi-Diameter | 15'23.6" |
| Moon Equatorial Horizontal Parallax | 0°56'29.6" |
| ΔT | 48.3 s |
This eclipse is part of aneclipse 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 afortnight.
| September 27 Descending node (full moon) | October 12 Ascending node (new moon) |
|---|---|
|  |
| Penumbral lunar eclipse Lunar Saros 117 | Total solar eclipse Solar Saros 143 |
This eclipse is a member of asemester series. An eclipse in a semester series of lunar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternatingnodes of the Moon's orbit.[5]
The penumbral lunar eclipse onJuly 27, 1980 occurs in the next lunar year eclipse set.
| Lunar eclipse series sets from 1977 to 1980 | ||||||||
|---|---|---|---|---|---|---|---|---|
| Ascending node | Descending node | |||||||
| Saros | Date Viewing | Type Chart | Gamma | Saros | Date Viewing | Type Chart | Gamma | |
| 112 | 1977 Apr 04 | Partial | −0.9148 | 117 | 1977 Sep 27 | Penumbral | 1.0768 | |
| 122 | 1978 Mar 24 | Total | −0.2140 | 127 | 1978 Sep 16 | Total | 0.2951 | |
| 132 | 1979 Mar 13 | Partial | 0.5254 | 137 | 1979 Sep 06 | Total | −0.4305 | |
| 142 | 1980 Mar 01 | Penumbral | 1.2270 | 147 | 1980 Aug 26 | Penumbral | −1.1608 | |
This eclipse is a part ofSaros series 117, repeating every 18 years, 11 days, and containing 71 events. The series started with a penumbral lunar eclipse on April 3, 1094. It contains partial eclipses from June 29, 1238 through September 23, 1382; total eclipses from October 3, 1400 through June 21, 1815; and a second set of partial eclipses from July 2, 1833 throughSeptember 5, 1941. The series ends at member 71 as a penumbral eclipse on May 15, 2356.
The longest duration of totality was produced by member 35 at 105 minutes, 43 seconds on April 17, 1707. All eclipses in this series occur at the Moon’sdescending node of orbit.[6]
| Greatest | First | |||
|---|---|---|---|---|
| The greatest eclipse of the series occurred on1707 Apr 17, lasting 105 minutes, 43 seconds.[7] | Penumbral | Partial | Total | Central |
| 1094 Apr 03 | 1238 Jun 29 | 1400 Oct 03 | 1563 Jan 09 | |
| Last | ||||
| Central | Total | Partial | Penumbral | |
| 1761 May 18 | 1815 Jun 21 | 1941 Sep 05 | 2356 May 15 | |
Eclipses are tabulated in three columns; every third eclipse in the same column is oneexeligmos apart, so they all cast shadows over approximately the same parts of the Earth.
| Series members 41–62 occur between 1801 and 2200: | |||||
|---|---|---|---|---|---|
| 41 | 42 | 43 | |||
| 1815 Jun 21 | 1833 Jul 02 | 1851 Jul 13 | |||
| 44 | 45 | 46 | |||
| 1869 Jul 23 | 1887 Aug 03 | 1905 Aug 15 | |||
 |  | ||||
| 47 | 48 | 49 | |||
| 1923 Aug 26 | 1941 Sep 05 | 1959 Sep 17 | |||
 |  | |  |  |  |
| 50 | 51 | 52 | |||
| 1977 Sep 27 | 1995 Oct 08 | 2013 Oct 18 | |||
| |  |  |  |  |
| 53 | 54 | 55 | |||
| 2031 Oct 30 | 2049 Nov 09 | 2067 Nov 21 | |||
 |  |  |  |  |  |
| 56 | 57 | 58 | |||
| 2085 Dec 01 | 2103 Dec 13 | 2121 Dec 24 | |||
| 59 | 60 | 61 | |||
| 2140 Jan 04 | 2158 Jan 14 | 2176 Jan 26 | |||
| 62 | |||||
| 2194 Feb 05 | |||||
This eclipse is a part of atritos cycle, repeating at alternating nodes every 135synodic months (≈ 3986.63 days, or 11 years minus 1 month). Their appearance and longitude are irregular due to a lack of synchronization with theanomalistic 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.
| Series members between 1801 and 2200 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1803 Feb 06 (Saros 101) | 1814 Jan 06 (Saros 102) | 1824 Dec 06 (Saros 103) | 1846 Oct 04 (Saros 105) | ||||||
| 1857 Sep 04 (Saros 106) | 1868 Aug 03 (Saros 107) | 1879 Jul 03 (Saros 108) | 1890 Jun 03 (Saros 109) | 1901 May 03 (Saros 110) | |||||
 |  | ||||||||
| 1912 Apr 01 (Saros 111) | 1923 Mar 03 (Saros 112) | 1934 Jan 30 (Saros 113) | 1944 Dec 29 (Saros 114) | 1955 Nov 29 (Saros 115) | |||||
 |  |  |  |  |  |  |  |  |  |
| 1966 Oct 29 (Saros 116) | 1977 Sep 27 (Saros 117) | 1988 Aug 27 (Saros 118) | 1999 Jul 28 (Saros 119) | 2010 Jun 26 (Saros 120) | |||||
 |  | | |  |  |  |  |  |  |
| 2021 May 26 (Saros 121) | 2032 Apr 25 (Saros 122) | 2043 Mar 25 (Saros 123) | 2054 Feb 22 (Saros 124) | 2065 Jan 22 (Saros 125) | |||||
 |  |  |  |  |  |  |  | ||
| 2075 Dec 22 (Saros 126) | 2086 Nov 20 (Saros 127) | 2097 Oct 21 (Saros 128) | 2108 Sep 20 (Saros 129) | 2119 Aug 20 (Saros 130) | |||||
| 2130 Jul 21 (Saros 131) | 2141 Jun 19 (Saros 132) | 2152 May 18 (Saros 133) | 2163 Apr 19 (Saros 134) | 2174 Mar 18 (Saros 135) | |||||
| 2185 Feb 14 (Saros 136) | 2196 Jan 15 (Saros 137) | ||||||||
This eclipse is a part of the long periodinex cycle, repeating at alternating nodes, every 358synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with theanomalistic 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.
| Series members between 1801 and 2200 | |||||
|---|---|---|---|---|---|
| 1804 Jan 26 (Saros 111) | 1833 Jan 06 (Saros 112) | 1861 Dec 17 (Saros 113) | |||
| 1890 Nov 26 (Saros 114) | 1919 Nov 07 (Saros 115) | 1948 Oct 18 (Saros 116) | |||
 |  |  |  | ||
| 1977 Sep 27 (Saros 117) | 2006 Sep 07 (Saros 118) | 2035 Aug 19 (Saros 119) | |||
| |  |  |  |  |
| 2064 Jul 28 (Saros 120) | 2093 Jul 08 (Saros 121) | 2122 Jun 20 (Saros 122) | |||
| 2151 May 30 (Saros 123) | 2180 May 09 (Saros 124) | ||||
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (ahalf saros).[8] This lunar eclipse is related to two solar eclipses ofSolar Saros 124.
| September 22, 1968 | October 3, 1986 |
|---|---|
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