Penumbral Lunar Eclipse of 1981 Jan 20

Fred Espenak

Introduction

The Penumbral Lunar Eclipse of 1981 Jan 20 is visible from the following geographic regions:

eastern Asia, Americas, Europe, northwestern Africa

The diagram to the right depicts the Moon's path with respect to Earth's umbral and penumbral shadows. Below it is a map showing the geographic regions of eclipse visibility. Click on the figure to enlarge it. For an explanation of the features appearing in the figure, see Key to Lunar Eclipse Figures.

The instant of greatest eclipse takes place on 1981 Jan 20 at 07:50:48 TD (07:49:57 UT1). This is 5.2 days after the Moon reaches perigee. During the eclipse, the Moon is in the constellation Cancer. The synodic month in which the eclipse takes place has a Brown Lunation Number of 718.

The eclipse belongs to Saros 114 and is number 57 of 71 eclipses in the series. All eclipses in this series occur at the Moon’s ascending node. The Moon moves southward with respect to the node with each succeeding eclipse in the series and gamma decreases.

This very deep penumbral eclipse is a rare total penumbral eclipse in which the entire disk of the Moon is immersed in the penumbral shadow. It has a penumbral eclipse magnitude of 1.0136 and a penumbral eclipse duration of 263.9 minutes. Gamma has a value of -1.0142.

The penumbral lunar eclipse of 1981 Jan 20 is followed two weeks later by a annular solar eclipse on 1981 Feb 04.

These eclipses all take place during a single eclipse season.

The eclipse predictions are given in both Terrestrial Dynamical Time (TD) and Universal Time (UT1). The parameter ΔT is used to convert between these two times (i.e., TD = UT1 + ΔT). ΔT has a value of 51.4 seconds for this eclipse.

The following links provide maps and data for the eclipse.

Detailed Lunar Eclipse Figure - eclipse geometry diagram and map of eclipse visibility (Key to Figure)
Saros 114 Table - data for all eclipses in the Saros series

The tables below contain detailed predictions and additional information on the Penumbral Lunar Eclipse of 1981 Jan 20 .

Eclipse Data: Penumbral Lunar Eclipse of 1981 Jan 20

Eclipse Characteristics
Parameter	Value
Penumbral Magnitude	1.01360
Umbral Magnitude	-0.01916
Gamma	-1.01421
Epsilon	0.9762°

Opposition Times
Event	Calendar Date & Time	Julian Date
Greatest Eclipse	1981 Jan 20 at 07:50:48.1 TD (07:49:56.7 UT1)	2444624.826351
Ecliptic Opposition	1981 Jan 20 at 07:39:48.6 TD (07:38:57.2 UT1)	2444624.818717
Equatorial Opposition	1981 Jan 20 at 08:03:57.5 TD (08:03:06.1 UT1)	2444624.835487

Geocentric Coordinates of Sun and Moon
1981 Jan 20 at 07:50:48.1 TD (07:49:56.7 UT1)
Coordinate	Sun	Moon
Right Ascension	20h09m28.4s	08h08m59.5s
Declination	-20°06'46.4"	+19°08'35.7"
Semi-Diameter	16'15.2"	15'44.3"
Eq. Hor. Parallax	08.9"	0°57'45.5"

Geocentric Libration of Moon
Angle	Value
l	4.9°
b	1.3°
c	13.8°

Earth's Shadows
Parameter	Value
Penumbral Radius	1.2456°
Umbral Radius	0.7039°

Prediction Paramaters
Paramater	Value
Ephemerides	JPL DE405
ΔT	51.4 s
Shadow Rule	Danjon
Shadow Enlargement	1.010
Saros Series	114 (57/71)

Explanation of Lunar Eclipse Data Tables

Eclipse Contacts: Penumbral Lunar Eclipse of 1981 Jan 20

Lunar Eclipse Contacts
Eclipse Event	Contact	Time TD	Time UT1	Zenith Latitude	Zenith Longitude	Position Angle	Axis Distance
Penumbral Begins	P1	05:38:48.1	05:37:56.6	19°17.5'N	083°03.9'W	236.4°	1.5091°
Greatest Eclipse	Greatest	07:50:48.1	07:49:56.7	19°08.6'N	114°50.9'W	186.7°	0.9762°
Penumbral Ends	P4	10:02:43.2	10:01:51.7	18°59.2'N	146°36.9'W	137.1°	1.5068°

Eclipse Durations
Eclipse Phase	Duration
Penumbral (P4 - P1)	04h23m55.1s

Explanation of Lunar Eclipse Contacts Table

Polynomial Besselian Elements: Penumbral Lunar Eclipse of 1981 Jan 20

Polynomial Besselian Elements
1981 Jan 20 at 08:00:00.0 TD (=t0)
n	x	y	d	f1	f2	f3
0	-0.03423	-0.97889	-0.3510	1.24557	0.70379	0.26228
1	0.51880	-0.06090	0.0002	-0.00042	-0.00042	-0.00011
2	-0.00025	-0.00006	0.0000	-0.00000	-0.00000	-0.00000
3	-0.00001	0.00000	-	-	-	-

At time t1 (decimal hours), each besselian element is evaluated by:

x = x0 + x1*t + x2*t² + x3*t³ (or x = Σ [xn*tⁿ]; n = 0 to 3)

where: t = t1 - t0 (decimal hours) and t0 = 8.000

Explanation of Besselian Elements

Eclipse Publications

For more visit: AstroPixels Publishing

Links for the Penumbral Lunar Eclipse of 1981 Jan 20

Detailed Lunar Eclipse Figure - eclipse geometry figure and map of eclipse visibility using Danjon method
Saros 114 Table - data for all eclipses in the Saros series
Penumbral Lunar Eclipse of 1981 Jan 20 - Google search for links to this eclipse

Links to Additional Lunar Eclipse Information

Home - home page of EclipseWise with predictions for both solar and lunar eclipses

Lunar Eclipses - primary page for lunar eclipse predictions
Lunar Eclipse Links - detailed directory of links

• Decade Tables of Lunar Eclipses:
| 1901 - 1910 | 1911 - 1919 | 1921 - 1930 | 1931 - 1940 | 1941 - 1950 |
| 1951 - 1960 | 1961 - 1970 | 1971 - 1980 | 1981 - 1990 | 1991 - 2000 |
| 2001 - 2010 | 2011 - 2020 | 2021 - 2030 | 2031 - 2040 | 2041 - 2050 |
| 2051 - 2060 | 2061 - 2070 | 2071 - 2080 | 2081 - 2090 | 2091 - 2100 |

Six Millennium Catalog of Lunar Eclipses - covers the years -2999 to +3000 (3000 BCE to 3000 CE)
Saros Catalog of Lunar Eclipses - covers Saros series -29 through 190
Javascript Lunar Eclipse Explorer - calculate all lunar eclipses visible from a city

Lunar Eclipse Basics - the fundamentals about lunar eclipses
Visual Appearance of Lunar Eclipses - describes how different types of lunar eclipses appear
Danjon Scale of Lunar Eclipse Brightness - evaluating the brightness of total lunar eclipses
Enlargement of Earth's Shadows (Herald and Sinnott method) - the effect on lunar eclipse predictions
Enlargement of Earth's Shadows (Danjon method) - the effect on lunar predictions

MrEclipse.com - Eclipse resources and tips on photography
MrEclipse: Lunar Eclipses for Beginners - a primer on solar eclipse basics
How to Photograph a Lunar Eclipse - instructions for imaging an eclipse of the Moon
MrEclipse Photo Index - an index of lunar eclipse photographs

Lunar Eclipse Publications

Eclipse Almanac: 2021 to 2030 - all solar and lunar eclipses for the decade
21st Century Canon of Lunar Eclipses - every lunar eclipse from 2001 through 2100
Thousand Year Canon of Lunar Eclipses 1501 to 2500 - basic details about every lunar eclipse for 1000 years
Five Millennium Canon of Lunar Eclipses: -1999 to +3000 - the ultimate reference with maps and diagrams
Five Millennium Catalog of Lunar Eclipses: -1999 to +3000 - the ultimate reference containing comprehensive tables

Eclipse Predictions

Predictions for the Penumbral Lunar Eclipse of 1981 Jan 20 were generated using the JPL DE405 solar and lunar ephemerides. The lunar coordinates were calculated with respect to the Moon's Center of Mass.

The Earth's umbral and penumbral shadows were calculated using the Danjon methodusing a mean mid-latitude ellipticity to compensate for the opacity of the terrestrial atmosphere.

The predictions are given in both Terrestrial Dynamical Time (TD) and Universal Time (UT1). The parameter ΔT is used to convert between these two times (i.e., UT1 = TD - ΔT). ΔT has a value of 51.4 seconds for this eclipse.

Acknowledgments

Some of the content on this web site is based on the book 21st Century Canon of Lunar Eclipses. All eclipse calculations are by Fred Espenak, and he assumes full responsibility for their accuracy.

Permission is granted to reproduce eclipse data when accompanied by a link to this page and an acknowledgment:

"Eclipse Predictions by Fred Espenak, www.EclipseWise.com"

The use of diagrams and maps is permitted provided that they are NOT altered (except for re-sizing) and the embedded credit line is NOT removed or covered.