Solar eclipse of April 18, 1977

There were 8 solar eclipses (at 6 month intervals) between May 11, 1975 and October 2, 1978.

Solar eclipse series sets from 1975–1978
Descending node				Ascending node
Saros	Map	Gamma		Saros	Map	Gamma
118	1975 May 11 Partial	1.06472		123	1975 November 3 Partial	-1.02475
128	1976 April 29 Annular	0.33783		133	1976 October 23 Total	-0.32699
138	1977 April 18 Annular	-0.39903		143	1977 October 12 Total	0.38363
148	1978 April 7 Partial	-1.10812		153	1978 October 2 Partial	1.16164

It is a part of Saros cycle 138, repeating every 18 years, 11 days, containing 70 events. The series started with partial solar eclipse on June 6, 1472. It contains annular eclipses from August 31, 1598 through February 18, 2482 with a hybrid eclipse on March 1, 2500. It has total eclipses from March 12, 2518 through April 3, 2554. The series ends at member 70 as a partial eclipse on July 11, 2716. The longest duration of totality will be only 56 seconds on April 3, 2554.

Series members 25–35 occur between 1901 and 2100:
25	26	27
March 6, 1905	March 17, 1923	March 27, 1941
28	29	30
April 8, 1959	April 18, 1977	April 29, 1995
31	32	33
May 10, 2013	May 21, 2031	May 31, 2049
34	35
June 11, 2067	June 22, 2085

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)

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	158	160	162
September 11, 2007	July 1, 2011	April 18, 2015	February 4, 2019	November 23, 2022