A total solar eclipse occurred at the Moon's ascending node of orbit on Tuesday, October 1, 1940,[1] with a magnitude of 1.0645. 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. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. Occurring only about 4 hours before perigee (on October 1, 1940, at 17:00 UTC), the Moon's apparent diameter was larger.[2]
Totality was visible from Colombia, Brazil, Venezuela and South Africa. A partial eclipse was visible for parts of the Caribbean, South America, Central Africa, and Southern Africa.
Members of the Joint Permanent Eclipse Committee of the Royal Society and Royal Astronomical Society made observations in Brazil with interferometers and spectrometers. Teams of the Royal Observatory, Greenwich and Royal Observatory, Cape of Good Hope (now combined into the South African Astronomical Observatory) went to Calvinia, South Africa to study the gravitational lens proposed by the general relativity. Other scientists went to the edge of the path of totality to study the spectral lines of the solar chromosphere. A joint team of the Heliophysical Observatory of the University of Cambridge and the Radcliffe Observatory in Pretoria, South Africa (now combined into the South African Astronomical Observatory) went to Nelspoort to study the extreme ultraviolet spectrum of the chromosphere and corona, and conducted polarization studies of the corona and sky around the sun.[3]
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.[4]
| First Penumbral External Contact | 1940 October 01 at 10:08:37.5 UTC | |
| First Umbral External Contact | 1940 October 01 at 11:03:28.3 UTC | |
| First Central Line | 1940 October 01 at 11:04:45.3 UTC | |
| First Umbral Internal Contact | 1940 October 01 at 11:06:02.4 UTC | |
| First Penumbral Internal Contact | 1940 October 01 at 12:04:11.7 UTC | |
| Ecliptic Conjunction | 1940 October 01 at 12:41:28.7 UTC | |
| Greatest Eclipse | 1940 October 01 at 12:44:06.1 UTC | |
| Greatest Duration | 1940 October 01 at 12:45:03.9 UTC | |
| Equatorial Conjunction | 1940 October 01 at 12:52:28.6 UTC | |
| Last Penumbral Internal Contact | 1940 October 01 at 13:23:47.3 UTC | |
| Last Umbral Internal Contact | 1940 October 01 at 14:22:03.5 UTC | |
| Last Central Line | 1940 October 01 at 14:23:20.8 UTC | |
| Last Umbral External Contact | 1940 October 01 at 14:24:38.0 UTC | |
| Last Penumbral External Contact | 1940 October 01 at 15:19:30.5 UTC |
| Eclipse Magnitude | 1.06446 | |
| Eclipse Obscuration | 1.13307 | |
| Gamma | −0.25727 | |
| Sun Right Ascension | 12h30m03.1s | |
| Sun Declination | -03°14'42.9" | |
| Sun Semi-Diameter | 15'58.8" | |
| Sun Equatorial Horizontal Parallax | 08.8" | |
| Moon Right Ascension | 12h29m44.0s | |
| Moon Declination | -03°29'44.3" | |
| Moon Semi-Diameter | 16'43.8" | |
| Moon Equatorial Horizontal Parallax | 1°01'24.1" | |
| ΔT | 24.7 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.