Solar eclipse of August 18, 1868
| Total eclipse | |
Map | |
| Gamma | −0.0443 |
|---|---|
| Magnitude | 1.0756 |
| Maximum eclipse | |
| Duration | 407 s (6 min 47 s) |
| Coordinates | 10°36′N 102°12′E / 10.6°N 102.2°E |
| Max. width of band | 245 km (152 mi) |
| Times (UTC) | |
| Greatest eclipse | 5:12:10 |
| References | |
| Saros | 133 (37 of 72) |
| Catalog # (SE5000) | 9207 |
A total solar eclipse occurred at the Moon's ascending node of orbit on Tuesday, August 18, 1868 (also known as "The King of Siam's eclipse"), with a magnitude of 1.0756. 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 about 6.5 days after perigee (on August 17, 1868, at 22:35 UTC), the Moon's apparent diameter was larger.
The path of totality was visible from parts of modern-day Ethiopia, Eritrea, Djibouti, Yemen, India, the Andaman and Nicobar Islands, Myanmar, Thailand, Cambodia, Vietnam, Malaysia, Brunei, Indonesia, and Papua New Guinea. A partial solar eclipse was also visible for parts of East Africa, the Middle East, Central Asia, South Asia, Southeast Asia, Australia, and western Oceania.
The total solar eclipse of 18 August 1868 was accurately predicted by King Mongkut of Siam, whose calculations were acknowledged as more precise than those of contemporary French astronomers. During observations of the eclipse, Pierre Janssen in Siam and, independently, Norman Lockyer in England detected a new yellow spectral line in the Sun's chromosphere using spectroscopes, leading to the discovery of the chemical element helium.