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Captain Cook and the transit of Venus

James Cook’s very first voyage to the Pacific in 1768 was funded by the Royal Society with the express purpose of observing the Transit of Venus from Tahiti. 

Edmund Halley.
View full size imageEdmund Halley (1656-1746), Astronomer Royal. © NMM

The idea of observing the transit from different places came from Sir Edmund Halley, the second Astronomer Royal.

In 1716, he suggested that if viewed simultaneously from different points on the globe, the transit could be used to determine the distance of the Earth from the Sun and so (with the help of Kepler’s equations) find the size of the Solar System. 

In 1761 the Royal Society sent the astronomers Nevil Maskelyne (later the 5th Astronomer Royal) and Robert Waddington to St Helena, and Charles Mason and Jeramiah Dixon to the Cape of Good Hope. Unfortunately, bad weather ruined the observations of Maskelyne and Waddington, so a comparison between the two observations could not be made. 

In 1769 the Royal Society funded and organised a new set of expeditions. This time, astronomers were sent to Hudson Bay, Cornwall, Ireland, Norway and Tahiti in the Pacific, to observe the second Transit of Venus that century. Lieutenant James Cook was chosen to command the expedition to Tahiti.

A replica of the tent used on the 1769 Transit of Venus expedition.

A replica of the tent used on the 1769 Transit of Venus expedition.
A replica of the tent used as a portable observatory on James Cook’s first voyage to the Pacific, a voyage that included the observation of the Transit of Venus of 1769 from Tahiti. The replica is shown with apparatus similar to what James Cook and his astronomer Charles Green might have used to view the transit. Green was a former employee of the Royal Observatory Greenwich.

A portable transit instrument.

A portable transit instrument.
A portable transit instrument similar to that used on James Cook’s Transit of Venus expedition of 1769. This telescope is made by Jesse Ramsden with optics by John Dollond. A very similar instrument, made by John Bird and belonging to the Royal Society, was taken in the 'Resolution' on Cook’s second voyage and in the 'Discovery' on the third voyage. The instrument shown here was probably made a few years after Bird’s, which does not seem to have survived.

Captain James Cook.

Captain James Cook.
This oil painting is the famous society portrait of Cook, which is widely reproduced. He is wearing a captain's full dress uniform of 1774-87, and a grey wig. A chart of the Southern Ocean lies on the table together with his hat. It was painted after Cook's second outstanding voyage for Sir Joseph Banks, in May 1776 and was presented to Greenwich Hospital by Banks's executor in 1829

Nevil Maskelyne (1732-1811), fifth Astronomer Royal.

Nevil Maskelyne (1732-1811), fifth Astronomer Royal.
A graduate of Trinity College, Cambridge, in 1761 Maskelyne was sent by the Royal Society to the island of St Helena to observe the transit of Venus. As Astronomer Royal (from 1765), he made improvements to existing apparatus and installed new equipment. In 1769 he used this to observe the transit of Venus at Greenwich. He was also involved in 'weighing the Earth'.

Transit of Venus

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