A total solar eclipse occurred at the Moon's descending node of orbit between Saturday, July 21 and Sunday, July 22, 1990,[1] with a magnitude of 1.0391. 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 2.7 days after perigee (on July 19, 1990, at 12:20 UTC), the Moon's apparent diameter was larger.[2]
Totality was visible in southern Finland including its capital city Helsinki, the Soviet Union (including today's northern Estonia and northern Russia), and eastern Andreanof Islands and Amukta of Alaska. A partial eclipse was visible for parts of Eastern Europe, North Asia, Alaska, western Canada, the western United States, and Hawaii.
In Finland, the solar eclipse occurred during sunrise and enabled observation and photography without protective glasses, which was however hampered by strong clouds.[3] The Sun was totally eclipsed in Helsinki began at 06:03:07 local time.
The Finnish Geodetic Institute conducted a series of measurements for 52 hours to study the changes in gravity using an absolute gravimeter in Helsinki. No abnormal values were recorded.[4] An observation team of the Academy of Sciences of the Soviet Union went to the Solovetsky Islands, Arkhangelsk Oblast in the White Sea, and planned to take images of the corona with different exposure levels and record videos. However, there were clouds at sunrise on the eclipse day, and drizzle continued until noon, so the observation was not successful.[5]
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.[6]
| First Penumbral External Contact | 1990 July 22 at 00:40:59.9 UTC | |
| First Umbral External Contact | 1990 July 22 at 01:53:08.5 UTC | |
| First Central Line | 1990 July 22 at 01:54:21.6 UTC | |
| First Umbral Internal Contact | 1990 July 22 at 01:55:35.5 UTC | |
| Equatorial Conjunction | 1990 July 22 at 02:37:42.8 UTC | |
| Ecliptic Conjunction | 1990 July 22 at 02:55:15.0 UTC | |
| Greatest Duration | 1990 July 22 at 03:00:36.7 UTC | |
| Greatest Eclipse | 1990 July 22 at 03:03:07.3 UTC | |
| Last Umbral Internal Contact | 1990 July 22 at 04:10:58.3 UTC | |
| Last Central Line | 1990 July 22 at 04:12:09.7 UTC | |
| Last Umbral External Contact | 1990 July 22 at 04:13:20.4 UTC | |
| Last Penumbral External Contact | 1990 July 22 at 05:25:30.2 UTC |
| Eclipse Magnitude | 1.03908 | |
| Eclipse Obscuration | 1.07968 | |
| Gamma | 0.75972 | |
| Sun Right Ascension | 08h04m51.4s | |
| Sun Declination | +20°20'48.2" | |
| Sun Semi-Diameter | 15'44.5" | |
| Sun Equatorial Horizontal Parallax | 08.7" | |
| Moon Right Ascension | 08h05m49.3s | |
| Moon Declination | +21°03'44.2" | |
| Moon Semi-Diameter | 16'11.1" | |
| Moon Equatorial Horizontal Parallax | 0°59'24.2" | |
| ΔT | 57.2 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.
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