Solar eclipse of October 12, 1977

A total solar eclipse occurred at the Moon's ascending node of orbit on Wednesday, October 12, 1977,^[1] with a magnitude of 1.0269. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. Occurring about 2.6 days before perigee (on October 15, 1977, at 10:00 UTC), the Moon's apparent diameter was larger.^[2]

Solar eclipse of October 12, 1977

Total eclipse
Map
Gamma	0.3836
Magnitude	1.0269
Maximum eclipse
Duration	157 s (2 min 37 s)
Coordinates	14.1°N 123.6°W / 14.1; -123.6
Max. width of band	99 km (62 mi)
Times (UTC)
Greatest eclipse	20:27:27
References
Saros	143 (21 of 72)
Catalog # (SE5000)	9459
← April 18, 1977 April 7, 1978 →

Totality was visible in the Pacific Ocean, Colombia and Venezuela. A partial eclipse was visible for parts of North America, Central America, the Caribbean, and northern South America.

Observations

The National Geographic Society funded an expedition by sea led by Jay Pasachoff from Williams College, Massachusetts to the northeast Pacific Ocean to observe the total eclipse. The team took images of the sky and corona during the totality phase as well as corona spectrum and infrared images.^[3]

Eclipse details

Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.^[4]

October 12, 1977 Solar Eclipse Times

Event	Time (UTC)
First Penumbral External Contact	1977 October 12 at 17:48:24.0 UTC
First Umbral External Contact	1977 October 12 at 18:48:59.6 UTC
First Central Line	1977 October 12 at 18:49:18.4 UTC
First Umbral Internal Contact	1977 October 12 at 18:49:37.3 UTC
First Penumbral Internal Contact	1977 October 12 at 20:01:41.4 UTC
Equatorial Conjunction	1977 October 12 at 20:15:17.1 UTC
Greatest Eclipse	1977 October 12 at 20:27:27.3 UTC
Greatest Duration	1977 October 12 at 20:30:55.5 UTC
Ecliptic Conjunction	1977 October 12 at 20:31:29.7 UTC
Last Penumbral Internal Contact	1977 October 12 at 20:53:33.8 UTC
Last Umbral Internal Contact	1977 October 12 at 22:05:23.4 UTC
Last Central Line	1977 October 12 at 22:05:44.5 UTC
Last Umbral External Contact	1977 October 12 at 22:06:05.6 UTC
Last Penumbral External Contact	1977 October 12 at 23:06:31.5 UTC

October 12, 1977 Solar Eclipse Parameters

Parameter	Value
Eclipse Magnitude	1.02694
Eclipse Obscuration	1.05462
Gamma	0.38363
Sun Right Ascension	13h11m36.7s
Sun Declination	-07°35'30.0"
Sun Semi-Diameter	16'01.8"
Sun Equatorial Horizontal Parallax	08.8"
Moon Right Ascension	13h12m03.0s
Moon Declination	-07°13'40.8"
Moon Semi-Diameter	16'12.7"
Moon Equatorial Horizontal Parallax	0°59'29.8"
ΔT	48.3 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 September–October 1977

September 27 Descending node (full moon)	October 12 Ascending node (new moon)
Penumbral lunar eclipse Lunar Saros 117	Total solar eclipse Solar Saros 143

Related eclipses

Eclipses in 1977

• A partial lunar eclipse on April 4.
• An annular solar eclipse on April 18.
• A penumbral lunar eclipse on September 27.
• A total solar eclipse on October 12.

Metonic

• Preceded by: Solar eclipse of December 24, 1973
• Followed by: Solar eclipse of July 31, 1981

Tzolkinex

• Preceded by: Solar eclipse of August 31, 1970
• Followed by: Solar eclipse of November 22, 1984

Half-Saros

• Preceded by: Lunar eclipse of October 6, 1968
• Followed by: Lunar eclipse of October 17, 1986

Tritos

• Preceded by: Solar eclipse of November 12, 1966
• Followed by: Solar eclipse of September 11, 1988

Solar Saros 143

• Preceded by: Solar eclipse of October 2, 1959
• Followed by: Solar eclipse of October 24, 1995

Inex

• Preceded by: Solar eclipse of November 1, 1948
• Followed by: Solar eclipse of September 22, 2006

Triad

• Preceded by: Solar eclipse of December 12, 1890
• Followed by: Solar eclipse of August 12, 2064

Solar eclipses of 1975–1978

This eclipse is a member of a semester series. An eclipse in a semester series of solar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.^[5]

Solar eclipse series sets from 1975 to 1978
Descending node				Ascending node
Saros	Map	Gamma		Saros	Map	Gamma
118	May 11, 1975 Partial	1.0647		123	November 3, 1975 Partial	−1.0248
128	April 29, 1976 Annular	0.3378		133	October 23, 1976 Total	−0.327
138	April 18, 1977 Annular	−0.399		143	October 12, 1977 Total	0.3836
148	April 7, 1978 Partial	−1.1081		153	October 2, 1978 Partial	1.1616

Saros 143

This eclipse is a part of Saros series 143, repeating every 18 years, 11 days, and containing 72 events. The series started with a partial solar eclipse on March 7, 1617. It contains total eclipses from June 24, 1797 through October 24, 1995; hybrid eclipses from November 3, 2013 through December 6, 2067; and annular eclipses from December 16, 2085 through September 16, 2536. The series ends at member 72 as a partial eclipse on April 23, 2897. Its 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.

The longest duration of totality was produced by member 16 at 3 minutes, 50 seconds on August 19, 1887, and the longest duration of annularity will be produced by member 51 at 4 minutes, 54 seconds on September 6, 2518. All eclipses in this series occur at the Moon’s ascending node of orbit.^[6]

Series members 12–33 occur between 1801 and 2200:
12	13	14
July 6, 1815	July 17, 1833	July 28, 1851
15	16	17
August 7, 1869	August 19, 1887	August 30, 1905
18	19	20
September 10, 1923	September 21, 1941	October 2, 1959
21	22	23
October 12, 1977	October 24, 1995	November 3, 2013
24	25	26
November 14, 2031	November 25, 2049	December 6, 2067
27	28	29
December 16, 2085	December 29, 2103	January 8, 2122
30	31	32
January 20, 2140	January 30, 2158	February 10, 2176
33
February 21, 2194

Metonic series

The metonic series repeats eclipses every 19 years (6939.69 days), lasting about 5 cycles. Eclipses occur in nearly the same calendar date. In addition, the octon subseries repeats 1/5 of that or every 3.8 years (1387.94 days). All eclipses in this table occur at the Moon's ascending node.

22 eclipse events between December 24, 1916 and July 31, 2000
December 24–25	October 12	July 31–August 1	May 19–20	March 7
111	113	115	117	119
December 24, 1916		July 31, 1924	May 19, 1928	March 7, 1932
121	123	125	127	129
December 25, 1935	October 12, 1939	August 1, 1943	May 20, 1947	March 7, 1951
131	133	135	137	139
December 25, 1954	October 12, 1958	July 31, 1962	May 20, 1966	March 7, 1970
141	143	145	147	149
December 24, 1973	October 12, 1977	July 31, 1981	May 19, 1985	March 7, 1989
151	153	155
December 24, 1992	October 12, 1996	July 31, 2000

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
February 21, 1803 (Saros 127)	January 21, 1814 (Saros 128)	December 20, 1824 (Saros 129)	November 20, 1835 (Saros 130)	October 20, 1846 (Saros 131)
September 18, 1857 (Saros 132)	August 18, 1868 (Saros 133)	July 19, 1879 (Saros 134)	June 17, 1890 (Saros 135)	May 18, 1901 (Saros 136)
April 17, 1912 (Saros 137)	March 17, 1923 (Saros 138)	February 14, 1934 (Saros 139)	January 14, 1945 (Saros 140)	December 14, 1955 (Saros 141)
November 12, 1966 (Saros 142)	October 12, 1977 (Saros 143)	September 11, 1988 (Saros 144)	August 11, 1999 (Saros 145)	July 11, 2010 (Saros 146)
June 10, 2021 (Saros 147)	May 9, 2032 (Saros 148)	April 9, 2043 (Saros 149)	March 9, 2054 (Saros 150)	February 5, 2065 (Saros 151)
January 6, 2076 (Saros 152)	December 6, 2086 (Saros 153)	November 4, 2097 (Saros 154)	October 5, 2108 (Saros 155)	September 5, 2119 (Saros 156)
August 4, 2130 (Saros 157)	July 3, 2141 (Saros 158)	June 3, 2152 (Saros 159)		April 1, 2174 (Saros 161)

Inex series

This eclipse is a part of the long period inex cycle, repeating at alternating nodes, every 358 synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic 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
February 11, 1804 (Saros 137)	January 20, 1833 (Saros 138)	December 31, 1861 (Saros 139)
December 12, 1890 (Saros 140)	November 22, 1919 (Saros 141)	November 1, 1948 (Saros 142)
October 12, 1977 (Saros 143)	September 22, 2006 (Saros 144)	September 2, 2035 (Saros 145)
August 12, 2064 (Saros 146)	July 23, 2093 (Saros 147)	July 4, 2122 (Saros 148)
June 14, 2151 (Saros 149)	May 24, 2180 (Saros 150)