January 1973 lunar eclipse

A penumbral lunar eclipse occurred at the Moon’s descending node of orbit on Thursday, January 18, 1973,^[1] with an umbral magnitude of −0.1292. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A penumbral lunar eclipse occurs when part or all of the Moon's near side passes into the Earth's penumbra. 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. Occurring about 2 days after perigee (on January 16, 1973, at 20:50 UTC), the Moon's apparent diameter was larger.^[2]

January 1973 lunar eclipse

Penumbral eclipse
The Moon's hourly motion shown right to left
Date	January 18, 1973
Gamma	−1.0845
Magnitude	−0.1292
Saros cycle	143 (16 of 73)
Penumbral	236 minutes, 29 seconds
Contacts (UTC) P1 19:18:59 Greatest 21:17:15 P4 23:15:27
← July 1972 June 1973 →

This eclipse was the first of four lunar eclipses in 1973, with the others occurring on June 15 (penumbral), July 15 (penumbral), and December 10 (partial).

Visibility

The eclipse was completely visible over Europe, Africa, and Asia, seen rising over eastern North America and much of South America and setting over east Asia and Australia.^[3]

Eclipse details

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

January 18, 1973 Lunar Eclipse Parameters

Parameter	Value
Penumbral Magnitude	0.86555
Umbral Magnitude	−0.12922
Gamma	−1.08446
Sun Right Ascension	20h03m09.2s
Sun Declination	-20°25'53.6"
Sun Semi-Diameter	16'15.4"
Sun Equatorial Horizontal Parallax	08.9"
Moon Right Ascension	08h01m47.2s
Moon Declination	+19°23'46.9"
Moon Semi-Diameter	16'20.5"
Moon Equatorial Horizontal Parallax	0°59'58.5"
ΔT	43.4 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 January 1973

January 4 Ascending node (new moon)	January 18 Descending node (full moon)
Annular solar eclipse Solar Saros 131	Penumbral lunar eclipse Lunar Saros 143

Related eclipses

Eclipses in 1973

• An annular solar eclipse on January 4.
• A penumbral lunar eclipse on January 18.
• A penumbral lunar eclipse on June 15.
• A total solar eclipse on June 30.
• A penumbral lunar eclipse on July 15.
• A partial lunar eclipse on December 10.
• An annular solar eclipse on December 24.

Metonic

• Preceded by: Lunar eclipse of April 2, 1969
• Followed by: Lunar eclipse of November 6, 1976

Tzolkinex

• Preceded by: Lunar eclipse of December 8, 1965
• Followed by: Lunar eclipse of March 1, 1980

Half-Saros

• Preceded by: Solar eclipse of January 14, 1964
• Followed by: Solar eclipse of January 25, 1982

Tritos

• Preceded by: Lunar eclipse of February 19, 1962
• Followed by: Lunar eclipse of December 20, 1983

Lunar Saros 143

• Preceded by: Lunar eclipse of January 8, 1955
• Followed by: Lunar eclipse of January 30, 1991

Inex

• Preceded by: Lunar eclipse of February 9, 1944
• Followed by: Lunar eclipse of December 30, 2001

Triad

• Preceded by: Lunar eclipse of March 20, 1886
• Followed by: Lunar eclipse of November 19, 2059

Lunar eclipses of 1969–1973

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 eclipses on April 2, 1969 and September 25, 1969 occur in the previous lunar year eclipse set, and the lunar eclipses on June 15, 1973 (penumbral) and December 10, 1973 (partial) occur in the next lunar year eclipse set.

Lunar eclipse series sets from 1969 to 1973
Ascending node					Descending node
Saros	Date Viewing	Type Chart	Gamma		Saros	Date Viewing	Type Chart	Gamma
108	1969 Aug 27	Penumbral	−1.5407		113	1970 Feb 21	Partial	0.9620
118	1970 Aug 17	Partial	−0.8053		123	1971 Feb 10	Total	0.2741
128	1971 Aug 06	Total	−0.0794		133	1972 Jan 30	Total	−0.4273
138	1972 Jul 26	Partial	0.7117		143	1973 Jan 18	Penumbral	−1.0845
148	1973 Jul 15	Penumbral	1.5178

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 penumbral lunar eclipse on August 18, 1720. It contains partial eclipses from March 14, 2063 through June 21, 2225; total eclipses from July 2, 2243 through April 13, 2712; and a second set of partial eclipses from April 25, 2730 through July 9, 2856. The series ends at member 72 as a penumbral eclipse on October 5, 3000.

The longest duration of totality will be produced by member 36 at 99 minutes, 9 seconds on September 6, 2351. 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 2351 Sep 06, lasting 99 minutes, 9 seconds.[7]	Penumbral	Partial	Total	Central
	1720 Aug 18	2063 Mar 14	2243 Jul 02	2297 Aug 03
	Last
	Central	Total	Partial	Penumbral
	2495 Dec 02	2712 Apr 13	2856 Jul 09	3000 Oct 05

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 6–27 occur between 1801 and 2200:
6		7		8
1810 Oct 12		1828 Oct 23		1846 Nov 03
9		10		11
1864 Nov 13		1882 Nov 25		1900 Dec 06
12		13		14
1918 Dec 17		1936 Dec 28		1955 Jan 08
15		16		17
1973 Jan 18		1991 Jan 30		2009 Feb 09
18		19		20
2027 Feb 20		2045 Mar 03		2063 Mar 14
21		22		23
2081 Mar 25		2099 Apr 05		2117 Apr 16
24		25		26
2135 Apr 28		2153 May 08		2171 May 19
27
2189 May 29

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 2147
1809 Apr 30 (Saros 128)		1820 Mar 29 (Saros 129)		1831 Feb 26 (Saros 130)		1842 Jan 26 (Saros 131)		1852 Dec 26 (Saros 132)
1863 Nov 25 (Saros 133)		1874 Oct 25 (Saros 134)		1885 Sep 24 (Saros 135)		1896 Aug 23 (Saros 136)		1907 Jul 25 (Saros 137)
1918 Jun 24 (Saros 138)		1929 May 23 (Saros 139)		1940 Apr 22 (Saros 140)		1951 Mar 23 (Saros 141)		1962 Feb 19 (Saros 142)
1973 Jan 18 (Saros 143)		1983 Dec 20 (Saros 144)		1994 Nov 18 (Saros 145)		2005 Oct 17 (Saros 146)		2016 Sep 16 (Saros 147)
2027 Aug 17 (Saros 148)		2038 Jul 16 (Saros 149)		2049 Jun 15 (Saros 150)
						2114 Dec 12 (Saros 156)
		2147 Sep 09 (Saros 159)

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
1828 Apr 29 (Saros 138)		1857 Apr 09 (Saros 139)		1886 Mar 20 (Saros 140)
1915 Mar 01 (Saros 141)		1944 Feb 09 (Saros 142)		1973 Jan 18 (Saros 143)
2001 Dec 30 (Saros 144)		2030 Dec 09 (Saros 145)		2059 Nov 19 (Saros 146)
2088 Oct 30 (Saros 147)		2117 Oct 10 (Saros 148)		2146 Sep 20 (Saros 149)
2175 Aug 31 (Saros 150)

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 partial solar eclipses of Solar Saros 150.

January 14, 1964	January 25, 1982

See also

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