An annular solar eclipse occurred at the Moon's ascending node of orbit on Thursday, January 4, 1973,[1] with a magnitude of 0.9303. 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. Occurring about 3.75 days after apogee (on December 31, 1972, at 21:50 UTC), the Moon's apparent diameter was smaller.[2]
Annularity was visible from Chile and Argentina. A partial eclipse was visible for parts of southern and central South America, Antarctica, West Africa, and Southern Africa.
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.[3]
| First Penumbral External Contact | 1973 January 04 at 12:44:40.6 UTC | |
| First Umbral External Contact | 1973 January 04 at 13:50:14.3 UTC | |
| First Central Line | 1973 January 04 at 13:53:17.7 UTC | |
| First Umbral Internal Contact | 1973 January 04 at 13:56:21.3 UTC | |
| First Penumbral Internal Contact | 1973 January 04 at 15:07:01.4 UTC | |
| Greatest Duration | 1973 January 04 at 15:35:51.4 UTC | |
| Equatorial Conjunction | 1973 January 04 at 15:39:50.9 UTC | |
| Ecliptic Conjunction | 1973 January 04 at 15:43:12.3 UTC | |
| Greatest Eclipse | 1973 January 04 at 15:46:20.7 UTC | |
| Last Penumbral Internal Contact | 1973 January 04 at 16:25:50.8 UTC | |
| Last Umbral Internal Contact | 1973 January 04 at 17:36:25.9 UTC | |
| Last Central Line | 1973 January 04 at 17:39:27.4 UTC | |
| Last Umbral External Contact | 1973 January 04 at 17:42:28.4 UTC | |
| Last Penumbral External Contact | 1973 January 04 at 18:47:58.6 UTC |
| Eclipse Magnitude | 0.93032 | |
| Eclipse Obscuration | 0.86549 | |
| Gamma | −0.26441 | |
| Sun Right Ascension | 19h01m31.4s | |
| Sun Declination | -22°41'24.6" | |
| Sun Semi-Diameter | 16'15.9" | |
| Sun Equatorial Horizontal Parallax | 08.9" | |
| Moon Right Ascension | 19h01m44.3s | |
| Moon Declination | -22°55'32.0" | |
| Moon Semi-Diameter | 14'54.7" | |
| Moon Equatorial Horizontal Parallax | 0°54'43.6" | |
| ΔT | 43.4 s |
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.