An annular solar eclipse occurred at the Moon's ascending node of orbit on Friday, December 14, 1917,[1] with a magnitude of 0.9791. 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 4.6 days before apogee (on December 18, 1917, at 22:10 UTC), the Moon's apparent diameter was smaller.[2]
This was the last of four solar eclipses in 1917, with the others occurring on January 23, June 19 and July 19.
The path of annularity crossed Antarctica. A partial eclipse was visible for parts of Antarctica, southern South America, and Australia. This annular eclipse is notable in that the path of annularity passed over the South Pole.
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 | 1917 December 14 at 07:09:48.7 UTC | |
| First Umbral External Contact | 1917 December 14 at 08:41:49.9 UTC | |
| First Central Line | 1917 December 14 at 08:43:56.6 UTC | |
| Greatest Duration | 1917 December 14 at 08:43:56.6 UTC | |
| First Umbral Internal Contact | 1917 December 14 at 08:46:08.6 UTC | |
| Ecliptic Conjunction | 1917 December 14 at 09:17:22.8 UTC | |
| Equatorial Conjunction | 1917 December 14 at 09:23:35.1 UTC | |
| Greatest Eclipse | 1917 December 14 at 09:27:19.7 UTC | |
| Last Umbral Internal Contact | 1917 December 14 at 10:08:36.2 UTC | |
| Last Central Line | 1917 December 14 at 10:10:45.3 UTC | |
| Last Umbral External Contact | 1917 December 14 at 10:12:49.1 UTC | |
| Last Penumbral External Contact | 1917 December 14 at 11:44:46.7 UTC |
| Eclipse Magnitude | 0.97913 | |
| Eclipse Obscuration | 0.95870 | |
| Gamma | –0.91566 | |
| Sun Right Ascension | 17h24m28.1s | |
| Sun Declination | -23°11'55.0" | |
| Sun Semi-Diameter | 16'15.0" | |
| Sun Equatorial Horizontal Parallax | 08.9" | |
| Moon Right Ascension | 17h24m36.7s | |
| Moon Declination | -24°04'53.4" | |
| Moon Semi-Diameter | 15'48.9" | |
| Moon Equatorial Horizontal Parallax | 0°58'02.6" | |
| ΔT | 20.2 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.