Monday, June 18, 2012

The Transit of Venus and the Parallax of the Sun

The Transit of Venus provided the first accurate value for the Sun's parallax which enables one to determine its distance. Edmond Halley proposed the method in a 1716 paper published in Philosophical Transactions, Vol. XXIX, No. 348, p. 454 and is written in Latin. There is an abridged English translation available at Google Books and a .pdf version online which includes a better view of the figure.
The paper suggests viewing the May 25, 1761 (O.S.) transit from different location on the Earth, viewing the entire transit from the north coast of Norway and using different locations to improve the opportunities for observation under poor weather conditions.
Supplemental (Jun 19): For an account of the observations see Newcomb, Popular Astronomy, p. 177.

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