An annular solar eclipse occurred at the Moon's descending node of orbit between Wednesday, February 4 and Thursday, February 5, 1981, 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).
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. 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.
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.
+February 4, 1981 Solar Eclipse Times 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
+February 4, 1981 Solar Eclipse Parameters 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
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–February 1981 January 20Ascending node (full moon) February 4Descending node (new moon) Penumbral lunar eclipseLunar Saros 114 Annular solar eclipseSolar 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
Saros 140
Metonic series
Tritos series
Inex series
Notes
References
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