Solar eclipse of 18 August 1868
| Solar eclipse of August 18, 1868 | |
|---|---|
Map
|
|
| Type of eclipse | |
| Nature | Total |
| Gamma | -0.0443 |
| Magnitude | 1.0756 |
| Maximum eclipse | |
| Duration | 407 sec (6 m 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 on August 18, 1868, also known as "The King of Siam's eclipse". 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.
Bullock sketch of the eclipse, Total Eclipses of the Sun, 1900.
M. Stephan sketches of the eclipse, Archives des missions scientifiques et littéraires, 1868.
Map of the forecast path of the total eclipse, Archives des missions scientifiques et littéraires, 1868.
Captain Bullock observed from the Celebes sea, sketching the appearance of the corona, while Gustav Fritsch accompanied an expedition to Aden.
French astronomer Pierre Janssen observed the eclipse from Guntur in Madras State, British India. It was the first total eclipse since Gustav Kirchhoff's 1859 theory that the Fraunhofer lines in the solar spectrum correspond to the emission line of the different chemical elements present in the Sun. Correspondingly, Janssen observed the eclipse with the aid of a spectroscope. He noticed a bright yellow line (λ = 587.49 nm) in the spectra of the solar prominences that could not be due to sodium as had previously been assumed, and was subsequently able to observe the same line even without the need for an eclipse. The same result was found independently by British astronomer Norman Lockyer, and both Janssen's and Lockyer's communications were presented to the French Academy of Sciences on October 26, 1868.
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