April 1968 lunar eclipse

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]

April 1968 lunar eclipse

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
Contacts (UTC) P1 2:12:37 U1 3:10:20 U2 4:23:08 Greatest 4:47:22 U3 5:11:38 U4 6:24:27 P4 7:22:07
← October 1967 October 1968 →

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.

Visibility

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]

Eclipse details

Shown below is a table displaying details about this particular solar eclipse. It describes various parameters pertaining to this eclipse.^[4]

April 13, 1968 Lunar Eclipse Parameters

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

Eclipse season

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.

Eclipse season of March–April 1968

March 28 Ascending node (new moon)	April 13 Descending node (full moon)
Partial solar eclipse Solar Saros 119	Total lunar eclipse Lunar Saros 131

Related eclipses

Eclipses in 1968

• A partial solar eclipse on March 28.
• A total lunar eclipse on April 13.
• A total solar eclipse on September 22.
• A total lunar eclipse on October 6.

Metonic

• Preceded by: Lunar eclipse of June 25, 1964
• Followed by: Lunar eclipse of January 30, 1972

Tzolkinex

• Preceded by: Lunar eclipse of March 2, 1961
• Followed by: Lunar eclipse of May 25, 1975

Half-Saros

• Preceded by: Solar eclipse of April 8, 1959
• Followed by: Solar eclipse of April 18, 1977

Tritos

• Preceded by: Lunar eclipse of May 13, 1957
• Followed by: Lunar eclipse of March 13, 1979

Lunar Saros 131

• Preceded by: Lunar eclipse of April 2, 1950
• Followed by: Lunar eclipse of April 24, 1986

Inex

• Preceded by: Lunar eclipse of May 3, 1939
• Followed by: Lunar eclipse of March 24, 1997

Triad

• Preceded by: Lunar eclipse of June 12, 1881
• Followed by: Lunar eclipse of February 11, 2055

Lunar eclipses of 1966–1969

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

Saros 131

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
31		32		33
1968 Apr 13		1986 Apr 24		2004 May 04
34		35		36
2022 May 16		2040 May 26		2058 Jun 06
37		38		39
2076 Jun 17		2094 Jun 28		2112 Jul 09
40		41		42
2130 Jul 21		2148 Jul 31		2166 Aug 11
43
2184 Aug 21

Tritos series

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)
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)
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)
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)
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)
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)

Inex series

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.

Series events from 1500–2500

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

Half-Saros cycle

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

See also

• List of lunar eclipses
• List of 20th-century lunar eclipses