From an observatory he constructed on Saint Helena in 1676–77, Halley catalogued the southern celestial hemisphere and recorded a transit of Mercury across the Sun.

Upon his return to England, he was made a fellow of the Royal Society, and with the help of King Charles II, was granted a master's degree from Oxford.

Halley encouraged and helped fund the publication of Isaac Newton's influential Philosophiæ Naturalis Principia Mathematica (1687).

[13] In 1676, Flamsteed helped Halley publish his first paper, titled "A Direct and Geometrical Method of Finding the Aphelia, Eccentricities, and Proportions of the Primary Planets, Without Supposing Equality in Angular Motion", about planetary orbits, in Philosophical Transactions of the Royal Society.

[13] Influenced by Flamsteed's project to compile a catalogue of stars of the northern celestial hemisphere, Halley proposed to do the same for the southern sky,[14] dropping out of school to do so.

He appealed to Charles II, who signed a letter requesting that Halley be unconditionally awarded his Master of Arts degree, which the college granted on 3 December 1678.

In early 1686, Halley was elected to the Royal Society's new position of secretary, requiring him to give up his fellowship and manage correspondence and meetings, as well as edit the Philosophical Transactions.

Halley asked to see the calculations and was told by Newton that he could not find them, but promised to redo them and send them on later, which he eventually did, in a short treatise titled On the motion of bodies in an orbit.

In 1691, Halley built a diving bell, a device in which the atmosphere was replenished by way of weighted barrels of air sent down from the surface.

[33] That same year, at a meeting of the Royal Society, Halley introduced a rudimentary working model of a magnetic compass using a liquid-filled housing to damp the swing and wobble of the magnetised needle.

While a candidate for the position, Halley faced the animosity of the Astronomer Royal, John Flamsteed, and the Anglican Church questioned his religious views,[f] largely on the grounds that he had doubted the Earth's age as given in the Bible.

[36] Halley's candidacy was opposed by both the Archbishop of Canterbury, John Tillotson, and Bishop Stillingfleet, and the post went instead to David Gregory, who had Newton's support.

He envisaged each inner region as having an atmosphere and being luminous (and possibly inhabited), and speculated that escaping gas caused the aurora borealis.

"[42] In 1693 Halley published an article on life annuities, which featured an analysis of age-at-death on the basis of the Breslau statistics Caspar Neumann had been able to provide.

[46] In 1698, at the behest of King William III, Halley was given command of the Paramour, a 52 feet (16 m) pink, so that he could carry out investigations in the South Atlantic into the laws governing the variation of the compass, as well as to refine the coordinates of the English colonies in the Americas.

[47] On 19 August 1698, he took command of the ship and, in November 1698, sailed on what was the first purely scientific voyage by an English naval vessel.

[48] Halley thereafter received a temporary commission as a captain in the Royal Navy, recommissioned the Paramour on 24 August 1699 and sailed again in September 1699 to make extensive observations on the conditions of terrestrial magnetism.

[51] The preface to Awnsham and John Churchill's collection of voyages and travels (1704), supposedly written by John Locke or by Halley, valourised expeditions such as these as part of a grand expansion of European knowledge of the world: What was cosmography before these discoveries, but an imperfect fragment of a science, scarce deserving so good a name?

Nay so great was the ignorance of man in this particular, that learned persons made a doubt of its being round; others no less knowing imagin'd all they were not acquainted with, desart and uninhabitable.

But now geography and hydrography have receiv'd some perfection by the pains of so many mariners and travelers, who to evince the rotundity of the earth and water, have sail’d and travell'd round it, as has been here made appear; to show there is no part uninhabitable, unless the frozen polar regions, have visited all other countries, tho never so remote, which they have found well peopl'd, and most of them rich and delightful….

Natural and moral history is embelish'd with the most beneficial increase of so many thousands of plants it had never before receiv'd, so many drugs and spices, such variety of beasts, birds and fishes, such rarities in minerals, mountains and waters, such unaccountable diversity of climates and men, and in them of complexions, tempers, habits, manners, politicks, and religions….

These and many more are the advantages drawn from the labours of those, who expose themselves to the dangers of the vast ocean, and of unknown nations; which those who sit still at home abundantly reap in every kind: and the relation of one traveler is an incentive to stir up another to imitate him, whilst the rest of mankind, in their accounts without stirring a foot, compass the earth and seas, visit all countries, and converse with all nations.

[52] In November 1703, Halley was appointed Savilian Professor of Geometry at the University of Oxford, his theological enemies, John Tillotson and Bishop Stillingfleet having died.

By 1706 Halley had learned Arabic and completed the translation started by Edward Bernard[55] of Books V–VII of Apollonius's Conics from copies found at Leiden and the Bodleian Library at Oxford.

Arcturus and Sirius were two noted to have moved significantly, the latter having progressed 30 arc minutes (about the diameter of the moon) southwards in 1800 years.

The idea can be tracked back to American astronomical texts such as William Augustus Norton's 1839 An Elementary Treatise on Astronomy, possibly due to Halley's royal occupations and connections to Sir Isaac Newton.

Contemporary accounts spell his name Hailey, Hayley, Haley, Haly, Halley, Hawley and Hawly, and presumably pronunciations varied similarly.