An annular solar eclipse occurred at the Moon's descending node of orbit on Thursday, September 7, 1820, with a magnitude of 0.9329. 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 only about 5 hours before apogee (on September 7, 1820, at 18:50 UTC), the Moon's apparent diameter was smaller.[1]
The path of annularity was visible from parts of modern-day northern Canada, Greenland, western Norway, Denmark, the Netherlands, Germany, Switzerland, the Czech Republic, Austria, Italy, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Albania, Greece, northeastern Libya, Egypt, Israel, Jordan, and Saudi Arabia. A partial solar eclipse was also visible for parts of northern North America, Europe, North Africa, the Middle East, and Central Asia.
This map was drawn in the book Elementa eclipsium, published in Prague in 1816, by Franz Ignaz Cassian Hallaschka (František Ignác Kassián Halaška) (1780-1847), contained maps of the paths of solar eclipses from 1816 and 1860. The geometric constructions used by Hallaschka anticipated the standard theory of eclipses later developed by Friedrich Wilhelm Bessel.[2]
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 | 1820 September 07 at 11:21:45.1 UTC | |
| First Umbral External Contact | 1820 September 07 at 12:48:53.2 UTC | |
| First Central Line | 1820 September 07 at 12:53:29.4 UTC | |
| First Umbral Internal Contact | 1820 September 07 at 12:58:19.3 UTC | |
| Equatorial Conjunction | 1820 September 07 at 13:06:52.6 UTC | |
| Ecliptic Conjunction | 1820 September 07 at 13:50:09.9 UTC | |
| Greatest Duration | 1820 September 07 at 13:57:39.4 UTC | |
| Greatest Eclipse | 1820 September 07 at 13:59:57.6 UTC | |
| Last Umbral Internal Contact | 1820 September 07 at 15:02:09.4 UTC | |
| Last Central Line | 1820 September 07 at 15:06:58.7 UTC | |
| Last Umbral External Contact | 1820 September 07 at 15:11:34.3 UTC | |
| Last Penumbral External Contact | 1820 September 07 at 16:38:31.5 UTC |
| Eclipse Magnitude | 0.93295 | |
| Eclipse Obscuration | 0.87040 | |
| Gamma | 0.82506 | |
| Sun Right Ascension | 11h04m02.1s | |
| Sun Declination | +05°59'29.3" | |
| Sun Semi-Diameter | 15'53.0" | |
| Sun Equatorial Horizontal Parallax | 08.7" | |
| Moon Right Ascension | 11h05m27.2s | |
| Moon Declination | +06°38'30.8" | |
| Moon Semi-Diameter | 14'41.9" | |
| Moon Equatorial Horizontal Parallax | 0°53'56.6" | |
| ΔT | 11.4 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.
The partial solar eclipses on April 24, 1819 and October 19, 1819 occur in the previous lunar year eclipse set, and the partial solar eclipses on January 12, 1823 and July 8, 1823 occur in the next lunar year eclipse set.
| Solar eclipse series sets from 1819 to 1823 | |||||||
|---|---|---|---|---|---|---|---|
| Ascending node | Descending node | ||||||
| Saros | Map | Gamma | Saros | Map | Gamma | ||
| 107 | March 25, 1819 Partial | −1.4722 | 112 | September 19, 1819 Partial | 1.5258 | ||
| 117 | March 14, 1820 Total | −0.7199 | 122 | September 7, 1820 Annular | 0.8251 | ||
| 127 | March 4, 1821 Total | −0.0284 | 132 | August 27, 1821 Annular | 0.0671 | ||
| 137 | February 21, 1822 Annular | 0.6914 | 142 | August 16, 1822 Total | −0.6904 | ||
| 147 | February 11, 1823 Partial | −1.5413 | 152 | August 6, 1823 Partial | 1.4546 | ||
All eclipses in this table occur at the Moon's descending node.
