Total lunar eclipse on April 13, 1968 From Wikipedia, the free encyclopedia
A total lunar eclipse occurred at the Moon’s descending node of orbit on Saturday, April 13, 1968,[1] with an umbral magnitude of 1.1116. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A total lunar eclipse occurs when the Moon's near side entirely passes into the Earth's umbral shadow. 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. A total lunar eclipse can last up to nearly two hours, while a total solar eclipse lasts only a few minutes at any given place, because the Moon's shadow is smaller. Occurring about 1.1 days before perigee (on April 14, 1968, at 7:50 UTC), the Moon's apparent diameter was larger.[2]
| Total eclipse | |||||||||||||||||
The Moon's hourly motion shown right to left | |||||||||||||||||
| Date | April 13, 1968 | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Gamma | −0.4173 | ||||||||||||||||
| Magnitude | 1.1116 | ||||||||||||||||
| Saros cycle | 131 (31 of 72) | ||||||||||||||||
| Totality | 48 minutes, 31 seconds | ||||||||||||||||
| Partiality | 194 minutes, 8 seconds | ||||||||||||||||
| Penumbral | 309 minutes, 30 seconds | ||||||||||||||||
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This lunar eclipse was the third of a tetrad, with four total lunar eclipses in series, the others being on April 24, 1967; October 18, 1967; and October 6, 1968.
The eclipse was completely visible over much of North America and South America, seen rising over northwestern North America and the central Pacific Ocean and setting over Europe, Africa, and the Middle East.[3]
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Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.[4]
| Parameter | Value |
|---|---|
| Penumbral Magnitude | 2.07253 |
| Umbral Magnitude | 1.11164 |
| Gamma | −0.41732 |
| Sun Right Ascension | 01h26m19.6s |
| Sun Declination | +09°03'48.7" |
| Sun Semi-Diameter | 15'56.9" |
| Sun Equatorial Horizontal Parallax | 08.8" |
| Moon Right Ascension | 13h25m32.2s |
| Moon Declination | -09°26'23.0" |
| Moon Semi-Diameter | 16'35.8" |
| Moon Equatorial Horizontal Parallax | 1°00'54.7" |
| ΔT | 38.5 s |
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.
| March 28 Ascending node (new moon) | April 13 Descending node (full moon) |
|---|---|
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| Partial solar eclipse Solar Saros 119 | Total lunar eclipse Lunar Saros 131 |
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.[5]
The penumbral lunar eclipse on August 27, 1969 occurs in the next lunar year eclipse set.
| Lunar eclipse series sets from 1966 to 1969 | ||||||||
|---|---|---|---|---|---|---|---|---|
| Descending node | Ascending node | |||||||
| Saros | Date Viewing |
Type Chart |
Gamma | Saros | Date Viewing |
Type Chart |
Gamma | |
| 111 | 1966 May 04 |
Penumbral |
1.0554 | 116 | 1966 Oct 29 |
Penumbral |
−1.0600 | |
| 121 | 1967 Apr 24 |
Total |
0.2972 | 126 | 1967 Oct 18 |
Total |
−0.3653 | |
| 131 | 1968 Apr 13 |
Total |
−0.4173 | 136 | 1968 Oct 06 |
Total |
0.3605 | |
| 141 | 1969 Apr 02 |
Penumbral |
−1.1765 | 146 | 1969 Sep 25 |
Penumbral |
1.0656 | |
This eclipse is a part of Saros series 131, repeating every 18 years, 11 days, and containing 72 events. The series started with a penumbral lunar eclipse on May 10, 1427. It contains partial eclipses from July 25, 1553 through March 22, 1932; total eclipses from April 2, 1950 through September 3, 2202; and a second set of partial eclipses from September 13, 2220 through April 9, 2563. The series ends at member 72 as a penumbral eclipse on July 7, 2707.
The longest duration of totality will be produced by member 38 at 100 minutes, 36 seconds on June 28, 2094. All eclipses in this series occur at the Moon’s descending node of orbit.[6]
| Greatest | First | |||
|---|---|---|---|---|
 The greatest eclipse of the series will occur on 2094 Jun 28, lasting 100 minutes, 36 seconds.[7] |
Penumbral | Partial | Total | Central |
| 1427 May 10 |
1553 Jul 25 |
1950 Apr 02 |
2022 May 16 | |
| Last | ||||
| Central | Total | Partial | Penumbral | |
| 2148 Jul 31 |
2202 Sep 03 |
2563 Apr 09 |
2707 Jul 07 | |
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.
| Series members 22–43 occur between 1801 and 2200: | |||||
|---|---|---|---|---|---|
| 22 | 23 | 24 | |||
| 1806 Jan 05 | 1824 Jan 16 | 1842 Jan 26 | |||
| 25 | 26 | 27 | |||
| 1860 Feb 07 | 1878 Feb 17 | 1896 Feb 28 | |||
| 28 | 29 | 30 | |||
| 1914 Mar 12 | 1932 Mar 22 | 1950 Apr 02 | |||
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| 31 | 32 | 33 | |||
| 1968 Apr 13 | 1986 Apr 24 | 2004 May 04 | |||
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| 34 | 35 | 36 | |||
| 2022 May 16 | 2040 May 26 | 2058 Jun 06 | |||
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| 37 | 38 | 39 | |||
| 2076 Jun 17 | 2094 Jun 28 | 2112 Jul 09 | |||
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| 40 | 41 | 42 | |||
| 2130 Jul 21 | 2148 Jul 31 | 2166 Aug 11 | |||
| 43 | |||||
| 2184 Aug 21 | |||||
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.
| Series members between 1801 and 2200 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1804 Jul 22 (Saros 116) |
1815 Jun 21 (Saros 117) |
1826 May 21 (Saros 118) |
1837 Apr 20 (Saros 119) |
1848 Mar 19 (Saros 120) | |||||
| 1859 Feb 17 (Saros 121) |
1870 Jan 17 (Saros 122) |
1880 Dec 16 (Saros 123) |
1891 Nov 16 (Saros 124) |
1902 Oct 17 (Saros 125) | |||||
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| 1913 Sep 15 (Saros 126) |
1924 Aug 14 (Saros 127) |
1935 Jul 16 (Saros 128) |
1946 Jun 14 (Saros 129) |
1957 May 13 (Saros 130) | |||||
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| 1968 Apr 13 (Saros 131) |
1979 Mar 13 (Saros 132) |
1990 Feb 09 (Saros 133) |
2001 Jan 09 (Saros 134) |
2011 Dec 10 (Saros 135) | |||||
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| 2022 Nov 08 (Saros 136) |
2033 Oct 08 (Saros 137) |
2044 Sep 07 (Saros 138) |
2055 Aug 07 (Saros 139) |
2066 Jul 07 (Saros 140) | |||||
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| 2077 Jun 06 (Saros 141) |
2088 May 05 (Saros 142) |
2099 Apr 05 (Saros 143) |
2110 Mar 06 (Saros 144) |
2121 Feb 02 (Saros 145) | |||||
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| 2132 Jan 02 (Saros 146) |
2142 Dec 03 (Saros 147) |
2153 Nov 01 (Saros 148) |
2164 Sep 30 (Saros 149) |
2175 Aug 31 (Saros 150) | |||||
| 2186 Jul 31 (Saros 151) |
2197 Jun 29 (Saros 152) | ||||||||
The inex series repeats eclipses 20 days short of 29 years, repeating on average every 10571.95 days. This period is equal to 358 lunations (synodic months) and 388.5 draconic months. Saros series increment by one on successive Inex events and repeat at alternate ascending and descending lunar nodes.
This period is 383.6734 anomalistic months (the period of the Moon's elliptical orbital precession). Despite the average 0.05 time-of-day shift between subsequent events, the variation of the Moon in its elliptical orbit at each event causes the actual eclipse time to vary significantly. It is a part of Lunar Inex series 35.
| Descending node | Ascending node | Descending node | Ascending node | ||||
|---|---|---|---|---|---|---|---|
| Saros | Date Chart |
Saros | Date Chart |
Saros | Date Chart |
Saros | Date Chart |
| 115 | 1505 Feb 18 |
116 | 1534 Jan 30 |
117 | 1563 Jan 9 | 118 | 1591 Dec 30 |
| 119 | 1620 Dec 9 | 120 | 1649 Nov 19 | 121 | 1678 Oct 29 | 122 | 1707 Oct 11 |
| 123 | 1736 Sep 20 | 124 | 1765 Aug 30 | 125 | 1794 Aug 11 | 126 | 1823 Jul 23 |
| 127 | 1852 Jul 1 | 128 | 1881 Jun 12 | 129 | 1910 May 24 |
130 | 1939 May 3 |
| 131 | 1968 Apr 13 |
132 | 1997 Mar 24 |
133 | 2026 Mar 3 |
134 | 2055 Feb 11 |
| 135 | 2084 Jan 22 |
136 | 2113 Jan 2 | 137 | 2141 Dec 13 | 138 | 2170 Nov 23 |
| 139 | 2199 Nov 2 | 140 | 2228 Oct 14 | 141 | 2257 Sep 24 | 142 | 2286 Sep 3 |
| 143 | 2315 Aug 16 | 144 | 2344 Jul 26 | 145 | 2373 Jul 5 | 146 | 2402 Jun 16 |
| 147 | 2431 May 27 | 148 | 2460 May 5 |
149 | 2489 Apr 16 | ||
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 annular solar eclipses of Solar Saros 138.
| April 8, 1959 | April 18, 1977 |
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