1769 transit of Venus observed from Tahiti

[2] These men, along with a crew of scientists, were commissioned by the Royal Society of London for the primary purpose of viewing the transit of Venus.

"[3] In 1663, Scottish mathematician James Gregory came up with the idea of using Venus or Mercury transits to determine the astronomical unit by measuring the apparent solar parallax between different points on the surface of the Earth.

[5] In a 1716 issue of the Philosophical Transactions of the Royal Society, Edmund Halley illustrated Gregory's theory more fully and explained further how it could establish the distance between the Earth and the Sun.

[8] Hornsby's publication in the Philosophical Transactions of the Royal Society in 1766 focused attention on the "cone of visibility" indicating, like Halley, some of the better places to observe the transit.

[8] The Royal Society boasted that the British "were inferior to no nation on earth, ancient or modern" and were eager to make another attempt.

The committee recommended that the transit be observed from three points: the North Cape at the Arctic tip of Norway, Fort Churchill at Hudson Bay Canada and a suitable island in the South Pacific.

Wallis returned from his voyage in time to help the Royal Society decide that it would be an ideal location to observe the Transit of Venus.

They were more interested in the "secret" mission that would be revealed after the Venus transit observation: the search for the alleged southern continent.

[11] Cook was considered the obvious choice as he was an outstanding seaman with navigational qualifications, a capable astronomer, and had observed a 1766 annular eclipse in Newfoundland that was communicated to the Royal Society by John Bevis.

A sandy spit on the northeast end of Matavai Bay, named Point Venus by Cook, was chosen for the site.

A gateway was assembled and within this fortification, fifty-four tents were pitched which housed the crew, scientists, and officers as well as the observatory, blacksmith equipment and a kitchen.

[15] In his journal, Cook wrote: This day prov'd as favourable to our purpose as we could wish, not a Clowd was to be seen the whole day and the Air was perfectly clear, so that we had every advantage we could desire in Observing the whole of the passage of the Planet Venus over the Suns disk: we very distinctly saw an Atmosphere or dusky shade round the body of the Planet which very much disturbed the times of the Contacts particularly the two internal ones.

[16] Recording the exact moment of the phases proved to be impossible due to a phenomenon called the "Black drop effect."

[2] For what they believed to be a failure in the observation, The Royal Society decided to blame Green who died on the voyage back to England.

Observations took place not only in Europe, but also included Calcutta, Tobolsk, Siberia, the Cape of Good Hope, and St. John's in Newfoundland.