Solar eclipse of February 4, 1981

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. This annular solar eclipse was large because the Moon covered 99.4% of the Sun, with a path width of only 25 km (15.534 mi, or 82,080.997 feet). 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). Occurring only 4 days before perigee (on February 8, 1981), the moon's apparent diameter was larger.

The moon's apparent diameter was 7 arcseconds smaller than the July 31, 1981 total solar eclipse.

Eclipse details

 * Eclipse Magnitude = 0.99375 (99.375%)
 * Eclipse Obscuration = 0.98754 (98.754%)
 * Greatest Eclipse = 1981 Feb 04 at 22:09:23.5 TD (22:08:32.1 UTC)
 * Ecliptic Conjunction = 1981 Feb 04 at 22:14:36.9 TD (22:13:45.5 UTC)
 * Equatorial Conjunction 1981 Feb 04 at 21:58:30.2 TD (21:57:38.8 UTC)
 * Gamma = -0.48375 (48.511%)
 * Sun's Right Ascension = 21.232
 * Sun's Declination = -16.03º
 * Sun's Diameter = 1946.4 arcseconds
 * Moon's Right Ascension = 21.239
 * Moon's Declination = -16.49º
 * Moon's Diameter = 1907.2 arcseconds
 * Moon's Distance = 375948.60 km (233603.63 mi)

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.

Eclipses in 1981

 * A penumbral lunar eclipse on January 20, 1981.
 * An annular solar eclipse on February 4, 1981.
 * A partial lunar eclipse on July 17, 1981.
 * A total solar eclipse on July 31, 1981.

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