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How Halley mapped the sky from St Helena

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A plague commemorates Edmund Halley at the remains of his observatory. Picture by John Grimshaw
A plaque commemorates Edmond Halley at the remains of his observatory. Picture by John Grimshaw

The astronomer Edmond Halley – famous for Halley’s Comet – spent a year on St Helena, creating the world’s first map of the stars over the Southern Hemisphere. JOHN GRIMSHAW tells the story.  

While still a student at Oxford University, Edmund Halley began to observe the heavens with the Astronomer Royal at Greenwich, John Flamsteed, only 10 years his senior, and published papers on sunspots and the solar system.

Influenced by Flamsteed’s project to compile a catalogue of northern stars, Halley proposed to do the same for the stars of the Southern Hemisphere, which had not at that time been observed.

St Helena was chosen being, then, the southern-most territory under British rule. King Charles II sent a letter to The East India Company desiring that Halley be granted free passage to St Helena and, without bothering to take his degree and aged 20, in November 1676, he sailed for Jamestown on the Indiaman Unity.

Halley took with him a great sextant specially constructed of five-and-a-half-foot radius fitted with telescopes in place of sights, his own two-foot quadrant, and several telescopes of different focal lengths up to 24 feet.

The weather in St. Helena proved less good for astronomical observations than Halley had hoped but despite this, by the time he returned home in 1678 he had recorded the celestial positions of 341 stars, which he published in his star catalogue on his return to England, along with a chart of the southern heavens.

On November 7th 1677 he also became the first astronomer to ever observe the complete transit of Mercury across the solar disc, but this came to naught when bad weather in England deprived him of the other half of the observations.

Even though he had left Oxford without a degree he quickly found himself considered among the top astronomers of the day. King Charles II decreed that the University of Oxford must confer a degree on Halley without him having to take the exams.

Later in 1678 he was also elected a member of the Royal Society and at the age of 22 one of its youngest members.

All these honours given to Halley did not sit well with John Flamsteed. Despite his earlier liking of the young college student, soon he considered him to be an enemy.

When, in 1720, he succeeded John Flamsteed as Astronomer Royal, Flamsteed’s widow was so angry that she had all of her late husband’s instruments sold so Halley could not use any of them.

He remained as Astronomer Royal until his death in 1742 at the age of 85, not surviving to see the predicted return of the comet, on 25 December 1758, which would later bear his name.

Halley returned briefly to St. Helena in 1700. Wanting more accurate magnetic charts of the Atlantic Ocean, their Lordships of the British Admiralty lent Halley a small sailing ship, the six-gun, three-masted, 52-foot Paramore, and instructed him to carry out a magnetic survey of the Atlantic Ocean and its bordering lands.

Perhaps considering this task an insufficient justification of the expedition, they also gave him a second one -“to stand soe farr into the South, till you discover the Coast of the Terra Incognita, supposed to lye between Magelan’s Streights and the Cape of Good Hope”.

The Paramore, the first ship built specifically as a research vessel for the Royal Navy, set out in October 1698 on what is regarded as the first sea voyage undertaken for a purely scientific endeavour, but was troubled by both leaks and by a personal conflict between Halley and the naval officer in charge of the ship.

Halley had the man arrested and turned the ship back to England, where a court of inquiry upheld him and gave him sole command of the ship.

The Paramore set out again in September 1699 and by 1 February 1700 the ship had penetrated the Antarctic Convergence to reach below 52 degrees latitude, only 90n miles north of South Georgia.

After this the ship continued to Tristan da Cunha, St Helena, Brazil, Barbados, Bermuda, Newfoundland and finally, at the end of August, back to England.

This article comes from John and Pauline Grimshaw’s collection of excellent St Helena pictures on the internet. See their flickr photostream, with historical notes, here

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