Solar eclipse of August 18, 1868
|Solar eclipse of August 18, 1868|
|Type of eclipse|
|Max. width of band||245 km|
|Saros||133 (37 of 72)|
|Catalog # (SE5000)||9207|
A total solar eclipse occurred on August 18, 1868. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partially 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, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across the surface of the Earth, while a partial solar eclipse will be visible over a region thousands of kilometres wide.
Discovery of helium 
French astronomer Pierre Janssen observed the eclipse from Guntur in Hyderabad State, British India. It was the first total eclipse since 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.
Mongkut's calculation 
Mongkut, King of Siam, was able to calculate and predict the solar eclipse two years earlier. The calculation was correct on the place, the time and the type of the solar eclipse that would happen. According to the Thai Astronomical Society, the international astronomical community calls the eclipse "King of Siam's eclipse".
Related eclipses 
It is a part of solar Saros 133.
- The Indian eclipse, 1898 Report of the expeditions organized by the British ... By Edward Walter Maunder, British Astronomical Association
- Standard Encyclopaedia of Southern Africa
- Leggett, Hadley (August 18, 2009), Aug. 18, 1868: Helium Discovered During Total Solar Eclipse, wired.com, retrieved 2010-03-18.
- C. R. Hebd. Acad. Sci. Paris 67, 1868: 836–41 http://gallica.bnf.fr/ark:/12148/bpt6k3024c.image.r=comptes-rendus+hebdomadaires+Acad%C3%A9mie+des+Sciences.f836.langFR
|url=missing title (help).
- ๒๐๐ ปี พระบาทสมเด็จพระจอมเกล้าเจ้าอยู่หัว พระบิดาแห่งวิทยาศาสตร์ไทย. (Thai)
- www.starwrite.org: Solar Astronomy in 1868
- Observations of the Total Solar Eclipse of August 18, 1868 by Charles G. Perrins
- Drawing of Corona
- Total Eclipses of the Sun, By Mabel Loomis Todd, 1894, new and revised edition by David P. Todd, 1900. 
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