Solar eclipse of April 18, 1977

Solar eclipse of April 18, 1977
Solar eclipse of April 18, 1977
	Map
Type of eclipse
Nature	Annular
Gamma	−0.399
Magnitude	0.9449
Maximum eclipse
Duration	424 s (7 min 4 s)
Coordinates	11°54′S 28°18′E / 11.9°S 28.3°E
Max. width of band	220 km (140 mi)
Times (UTC)
Greatest eclipse	10:31:30
References
Saros	138 (29 of 70)
Catalog # (SE5000)	9458

An annular solar eclipse occurred at the Moon's descending node of orbit on Monday, April 18, 1977, with a magnitude of 0.9449. 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. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in South West Africa (today's Namibia), Angola, Zambia, southeastern Zaire (today's Democratic Republic of Congo), northern Malawi, Tanzania, Seychelles and the whole British Indian Ocean Territory.

Related eclipses[edit]

Solar eclipses of 1975–1978[edit]

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.^[1]

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 138[edit]

This eclipse is a part of Saros series 138, repeating every 18 years, 11 days, and containing 70 events. The series started with a partial solar eclipse on June 6, 1472. It contains annular eclipses from August 31, 1598 through February 18, 2482; a hybrid eclipse on March 1, 2500; and total eclipses from March 12, 2518 through April 3, 2554. The series ends at member 70 as a partial eclipse on July 11, 2716. 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 annularity was produced by member 23 at 8 minutes, 2 seconds on February 11, 1869, and the longest duration of totality will be produced by member 61 at 56 seconds on April 3, 2554. All eclipses in this series occur at the Moon’s descending node of orbit.^[2]

Series members 20–41 occur between 1801 and 2200:
20	21	22
January 10, 1815	January 20, 1833	February 1, 1851
23	24	25
February 11, 1869	February 22, 1887	March 6, 1905
26	27	28
March 17, 1923	March 27, 1941	April 8, 1959
29	30	31
April 18, 1977	April 29, 1995	May 10, 2013
32	33	34
May 21, 2031	May 31, 2049	June 11, 2067
35	36	37
June 22, 2085	July 4, 2103	July 14, 2121
38	39	40
July 25, 2139	August 5, 2157	August 16, 2175
41
August 26, 2193

Inex series[edit]

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.

Inex series members between 1901 and 2100:
May 29, 1919 (Saros 136)	May 9, 1948 (Saros 137)	April 18, 1977 (Saros 138)
March 29, 2006 (Saros 139)	March 9, 2035 (Saros 140)	February 17, 2064 (Saros 141)
January 27, 2093 (Saros 142)

Metonic series[edit]

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 descending node.

22 eclipse events between September 12, 1931 and July 1, 2011.
September 11-12	June 30-July 1	April 17-19	February 4-5	November 22-23
114	116	118	120	122
September 12, 1931	June 30, 1935	April 19, 1939	February 4, 1943	November 23, 1946
124	126	128	130	132
September 12, 1950	June 30, 1954	April 19, 1958	February 5, 1962	November 23, 1965
134	136	138	140	142
September 11, 1969	June 30, 1973	April 18, 1977	February 4, 1981	November 22, 1984
144	146	148	150	152
September 11, 1988	June 30, 1992	April 17, 1996	February 5, 2000	November 23, 2003
154	156
September 11, 2007	July 1, 2011