Solar eclipse of February 4, 1981
Template:Short description Script error: No such module "Solar eclipse". An annular solar eclipse occurred at the Moon's descending node of orbit between Wednesday, February 4 and Thursday, February 5, 1981,[1] with a magnitude of 0.9937. 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. The Moon's apparent diameter was near the average diameter because it occurred 8.1 days after apogee (on January 27, 1981, at 20:30 UTC) and 4 days before perigee (on February 8, 1981, at 22:30 UTC).[2]
The moon's apparent diameter was 7 arcseconds smaller than the July 31, 1981 total solar eclipse.
It was visible in Australia, crossing over Tasmania and southern Stewart Island of New Zealand near sunrise on February 5 (Thursday), and ended at sunset over western South America on February 4 (Wednesday). A partial eclipse was visible for parts of Eastern Australia, Oceania, Antarctica, and western South America.
Observations
The Astronomical Society of Tasmania set up 18 observation sites on the northern and southern edges of the path of annularity in Tasmania to measure the diameter of the sun. However, data were obtained from only one site on the northern and one on the southern edge due to the clouds. The United States Naval Observatory also took images of the partial phase with portable video recorders in Tasmania.[3] Besides, due to the influence of the concave and convex peaks on the edge of the moon, if the moon is assumed to be a uniform sphere, the predicted times of each contact of the eclipse were slightly different from the actual times because the predictions assumed the moon to be a circular body but there are actually mountains and valleys on the lunar limb. The British Astronomical Association observed this eclipse in Tasmania and studied the methods to calculate the time of eclipses more accurately.[4]
Eclipse details
Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.[5]
| Event | Time (UTC) |
|---|---|
| First Penumbral External Contact | 1981 February 04 at 19:28:42.2 UTC |
| First Umbral External Contact | 1981 February 04 at 20:33:25.0 UTC |
| First Central Line | 1981 February 04 at 20:34:09.9 UTC |
| Greatest Duration | 1981 February 04 at 20:34:09.9 UTC |
| First Umbral Internal Contact | 1981 February 04 at 20:34:54.9 UTC |
| Equatorial Conjunction | 1981 February 04 at 21:58:30.2 UTC |
| Greatest Eclipse | 1981 February 04 at 22:09:23.5 UTC |
| Ecliptic Conjunction | 1981 February 04 at 22:14:36.9 UTC |
| Last Umbral Internal Contact | 1981 February 04 at 23:44:02.3 UTC |
| Last Central Line | 1981 February 04 at 23:44:44.4 UTC |
| Last Umbral External Contact | 1981 February 04 at 23:45:26.3 UTC |
| Last Penumbral External Contact | 1981 February 05 at 00:50:03.7 UTC |
| Parameter | Value |
|---|---|
| Eclipse Magnitude | 0.99375 |
| Eclipse Obscuration | 0.98754 |
| Gamma | −0.48375 |
| Sun Right Ascension | 21h13m55.8s |
| Sun Declination | -16°02'03.1" |
| Sun Semi-Diameter | 16'13.2" |
| Sun Equatorial Horizontal Parallax | 08.9" |
| Moon Right Ascension | 21h14m19.6s |
| Moon Declination | -16°29'36.7" |
| Moon Semi-Diameter | 15'53.6" |
| Moon Equatorial Horizontal Parallax | 0°58'19.6" |
| ΔT | 51.4 s |
Eclipse season
Script error: No such module "Labelled list hatnote". 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.
| January 20 Ascending node (full moon) |
February 4 Descending node (new moon) |
|---|---|
| File:Lunar eclipse chart close-1981Jan20.png | File:SE1981Feb04A.png |
| Penumbral lunar eclipse Lunar Saros 114 |
Annular solar eclipse Solar Saros 140 |
Related eclipses
Eclipses in 1981
- A penumbral lunar eclipse on January 20.
- An annular solar eclipse on February 4.
- A partial lunar eclipse on July 17.
- A total solar eclipse on July 31.
Metonic
- Preceded by: Solar eclipse of April 18, 1977
- Followed by: Solar eclipse of November 22, 1984
Tzolkinex
- Preceded by: Solar eclipse of December 24, 1973
- Followed by: Solar eclipse of March 18, 1988
Half-Saros
- Preceded by: Lunar eclipse of January 30, 1972
- Followed by: Lunar eclipse of February 9, 1990
Tritos
- Preceded by: Solar eclipse of March 7, 1970
- Followed by: Solar eclipse of January 4, 1992
Solar Saros 140
- Preceded by: Solar eclipse of January 25, 1963
- Followed by: Solar eclipse of February 16, 1999
Inex
- Preceded by: Solar eclipse of February 25, 1952
- Followed by: Solar eclipse of January 15, 2010
Triad
- Preceded by: Solar eclipse of April 6, 1894
- Followed by: Solar eclipse of December 6, 2067
Solar eclipses of 1979–1982
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.[6]
The partial solar eclipses on June 21, 1982 and December 15, 1982 occur in the next lunar year eclipse set.
| Solar eclipse series sets from 1979 to 1982 | ||||||
|---|---|---|---|---|---|---|
| Descending node | Ascending node | |||||
| Saros | Map | Gamma | Saros | Map | Gamma | |
| 120 File:1979 Solar eclipse, Brandon Manitoba Canada (35907221663).jpg Totality in Brandon, MB, Canada |
February 26, 1979 File:SE1979Feb26T.png Total |
0.8981 | 125 | August 22, 1979 File:SE1979Aug22A.png Annular |
−0.9632 | |
| 130 | February 16, 1980 File:SE1980Feb16T.png Total |
0.2224 | 135 | August 10, 1980 File:SE1980Aug10A.png Annular |
−0.1915 | |
| 140 | February 4, 1981 File:SE1981Feb04A.png Annular |
−0.4838 | 145 | July 31, 1981 File:SE1981Jul31T.png Total |
0.5792 | |
| 150 | January 25, 1982 File:SE1982Jan25P.png Partial |
−1.2311 | 155 | July 20, 1982 File:SE1982Jul20P.png Partial |
1.2886 | |
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Saros 140
Template:Solar Saros series 140
Metonic series
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.
Tritos series
Template:Solar Tritos series 2002 December 4
Inex series
Template:Solar Inex series 2010 January 15
Notes
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References
- Earth visibility chart and eclipse statistics Eclipse Predictions by Fred Espenak, NASA/GSFC
- Annular Solar Eclipse Observed for Solar Radius Determination Observed from Tasmania, by Fiala, A. D., Herald, D., & Dunham, D. W, Bulletin of the American Astronomical Society, Vol. 13, p. 552
- Correcting predictions of solar eclipse contact times for the effects of lunar limb irregularities Observations from Tasmania by Herald, D. Journal of the British Astronomical Association, vol.93, no.6, p. 241–246
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