A partial lunar eclipse occurred at the Moon’s descending node of orbit on Friday, July 17, 1981,[1] with an umbral magnitude of 0.5486. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A partial lunar eclipse occurs when one part of the Moon is in the Earth's umbra, while the other part is in 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 5.4 days after apogee (on July 11, 1981, at 18:35 UTC), the Moon's apparent diameter was smaller.[2]

Visibility

The eclipse was completely visible over central and eastern North America, South America, and Antarctica, seen rising over western North America and the central Pacific Ocean and setting over much of 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]

July 17, 1981 Lunar Eclipse Parameters
Parameter Value
Penumbral Magnitude 1.58223
Umbral Magnitude 0.54860
Gamma 0.70454
Sun Right Ascension 07h45m44.1s
Sun Declination +21°13'06.1"
Sun Semi-Diameter 15'44.2"
Sun Equatorial Horizontal Parallax 08.7"
Moon Right Ascension 19h45m30.8s
Moon Declination -20°33'51.6"
Moon Semi-Diameter 15'13.5"
Moon Equatorial Horizontal Parallax 0°55'52.6"
ΔT 51.9 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 July 1981
July 17
Descending node (full moon)
 July 31
Ascending node (new moon)
Partial lunar eclipse
Lunar Saros 119		 Total solar eclipse
Solar Saros 145

Eclipses in 1981

Metonic

Tzolkinex

Half-Saros

Tritos

Lunar Saros 119

Inex

Triad

Lunar eclipses of 1980–1984

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 March 1, 1980 and August 26, 1980 occur in the previous lunar year eclipse set, and the penumbral lunar eclipses on May 15, 1984 and November 8, 1984 occur in the next lunar year eclipse set.

Lunar eclipse series sets from 1980 to 1984
Descending node   Ascending node
Saros Date
Viewing 		Type
Chart 		Gamma Saros Date
Viewing 		Type
Chart 		Gamma
109 1980 Jul 27
 Penumbral
 1.4139 114 1981 Jan 20
 Penumbral
 −1.0142
119 1981 Jul 17
 Partial
 0.7045 124 1982 Jan 09
 Total
 −0.2916
129 1982 Jul 06
 Total
 −0.0579 134 1982 Dec 30
 Total
 0.3758
139 1983 Jun 25
 Partial
 −0.8152 144 1983 Dec 20
 Penumbral
 1.0747
149 1984 Jun 13
 Penumbral
 −1.5240

Saros 119

This eclipse is a part of Saros series 119, repeating every 18 years, 11 days, and containing 82 events. The series started with a penumbral lunar eclipse on October 14, 935 AD. It contains partial eclipses from May 18, 1296 through August 2, 1422; total eclipses from August 13, 1440 through June 15, 1927; and a second set of partial eclipses from June 25, 1945 through August 19, 2035. The series ends at member 82 as a penumbral eclipse on March 25, 2396.

The longest duration of totality was produced by member 49 at 102 minutes, 6 seconds on March 30, 1801. All eclipses in this series occur at the Moon’s descending node of orbit.[6]

Greatest First
The greatest eclipse of the series occurred on 1801 Mar 30, lasting 102 minutes, 6 seconds.[7] Penumbral Partial Total Central
934 Oct 14
 1296 May 18
 1440 Aug 13
 1512 Sep 25
Last
Central Total Partial Penumbral
1873 May 12
 1927 Jun 15
 2035 Aug 19
 2396 Mar 25

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.

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
1806 Nov 26
(Saros 103) 		1828 Sep 23
(Saros 105) 		1839 Aug 24
(Saros 106) 		1850 Jul 24
(Saros 107)
1861 Jun 22
(Saros 108) 		1872 May 22
(Saros 109) 		1883 Apr 22
(Saros 110) 		1894 Mar 21
(Saros 111) 		1905 Feb 19
(Saros 112)
1916 Jan 20
(Saros 113) 		1926 Dec 19
(Saros 114) 		1937 Nov 18
(Saros 115) 		1948 Oct 18
(Saros 116) 		1959 Sep 17
(Saros 117)
1970 Aug 17
(Saros 118) 		1981 Jul 17
(Saros 119) 		1992 Jun 15
(Saros 120) 		2003 May 16
(Saros 121) 		2014 Apr 15
(Saros 122)
2025 Mar 14
(Saros 123) 		2036 Feb 11
(Saros 124) 		2047 Jan 12
(Saros 125) 		2057 Dec 11
(Saros 126) 		2068 Nov 09
(Saros 127)
2079 Oct 10
(Saros 128) 		2090 Sep 08
(Saros 129) 		2101 Aug 09
(Saros 130) 		2112 Jul 09
(Saros 131) 		2123 Jun 09
(Saros 132)
2134 May 08
(Saros 133) 		2145 Apr 07
(Saros 134) 		2156 Mar 07
(Saros 135) 		2167 Feb 04
(Saros 136) 		2178 Jan 04
(Saros 137)
2188 Dec 04
(Saros 138) 		2199 Nov 02
(Saros 139)

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 total solar eclipses of Solar Saros 126.

July 10, 1972 July 22, 1990

See also

Notes

  1. ^ "July 16–17, 1981 Partial Lunar Eclipse". timeanddate. Retrieved 6 January 2025.
  2. ^ "Moon Distances for London, United Kingdom, England". timeanddate. Retrieved 6 January 2025.
  3. ^ "Partial Lunar Eclipse of 1981 Jul 17" (PDF). NASA. Retrieved 6 January 2025.
  4. ^ "Partial Lunar Eclipse of 1981 Jul 17". EclipseWise.com. Retrieved 6 January 2025.
  5. ^ van Gent, R.H. "Solar- and Lunar-Eclipse Predictions from Antiquity to the Present". A Catalogue of Eclipse Cycles. Utrecht University. Retrieved 6 October 2018.
  6. ^ "NASA - Catalog of Lunar Eclipses of Saros 119". eclipse.gsfc.nasa.gov.
  7. ^ Listing of Eclipses of series 119
  8. ^ Mathematical Astronomy Morsels, Jean Meeus, p.110, Chapter 18, The half-saros


Allikas: https://en.wikipedia.org/wiki/July_1981_lunar_eclipse
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