Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy Summary

  • Last updated on November 10, 2022

John Flamsteed’s catalog, and later atlas, of the locations of the stars more than doubled the number of stars accurately charted and established a standard used for more than a century by navigators and theoretical cosmologists.

Summary of Event

In 1725, a definitive catalog of the stars visible from Greenwich, England, appeared in three massive volumes titled Historia coelestis Britannica Historia coelestis Britannica (Flamsteed) (British Catalogue of the Heavens, British Catalogue of the Heavens (Flamsteed) partial translation, 1982). A fourth volume, Atlas coelestis Britannica, Atlas coelestis Britannica (Flamsteed) containing star charts, was published in 1729 in English. These books represented the life’s work of John Flamsteed, England’s first astronomer royal. Unfinished at his death in 1719, the catalog was prepared for publication by Flamsteed’s assistants, Abraham Sharp and Joseph Crosthwait, and his spouse, Margaret Flamsteed, who persevered despite financial setbacks and a lack of support from Flamsteed’s successor, astronomer Edmond Halley. [kw]Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy (1725) [kw]Astronomy, Flamsteed’s Star Catalog Marks the Transition to Modern (1725) [kw]Transition to Modern Astronomy, Flamsteed’s Star Catalog Marks the (1725) [kw]Catalog Marks the Transition to Modern Astronomy, Flamsteed’s Star (1725) [kw]Star Catalog Marks the Transition to Modern Astronomy, Flamsteed’s (1725) Star catalogs Astronomy;modern [g]England;1725: Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy[0650] [c]Astronomy;1725: Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy[0650] [c]Science and technology;1725: Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy[0650] Flamsteed, John Brahe, Tycho Flamsteed, Margaret Halley, Edmond Sharp, Abraham Crosthwait, Joseph

The first two volumes of Historia coelestis Britannica offered a detailed record of all of the observations made by Flamsteed at Derby and Greenwich between 1673 and 1713; the third volume was a catalog of the positions of more than three thousand stars visible from Greenwich. The star catalog represented a twofold increase in numbers beyond the catalog produced by Tycho Brahe more than a century earlier, with a corresponding increase in the precision with which the relative positions of the stars were recorded.

Flamsteed’s work as astronomer royal marked the final emancipation of observational astronomy from its astrological Astrology and theological roots. Brahe’s support depended on supplying horoscopes to his princely patron. The English amateur astronomer Jeremiah Horrocks, Horrocks, Jeremiah whose posthumous works Flamsteed helped edit, published landmark lunar observations in almanac form, coupling the lunar data with advice about human affairs. Flamsteed’s earliest work, a lunar ephemeris, was rejected by the publisher because it lacked astrological advice and thus, the publisher reasoned, would not sell.

King Charles II established the Royal Observatory, Greenwich, Royal Observatory, Greenwich, England in 1675 and authorized Flamsteed’s salary as first astronomer royal with a quite different and wholly scientific aim: to produce an accurate chart of the heavens for navigational Navigation;and astronomy[astronomy] Astronomy;and navigation[navigation] purposes. There was also an element of national pride involved in this first “space race.” The French, under King Louis XIV, had recently established a national observatory in Paris, and the English were loath to cede preeminence in knowledge of the heavens.

In an age of rapid colonial expansion, accurate determination of longitude Longitude at sea was becoming critical to navigators. The most promising avenues for doing so involved finding the time Time and navigation Navigation;and time[time] difference between a ship’s position and some fixed point, the challenge being to determine accurately, at a remote location, what time it was in England. The position of the Moon relative to stars, and eclipses of the moons of Jupiter, potentially afforded the requisite accuracy, but existing star charts and records of the lunar orbit were clearly inadequate. To produce an adequate chart required years of observation, using instrumentation that was constantly being refined.

The key to Flamsteed’s observations was a 7-foot mural arc, permanently oriented north-south along the Greenwich meridian Prime meridian and equipped with a telescopic sight. The size of the arc allowed for accurate calibration of angles, and the provision of a telescopic sight both increased the precision of alignment and permitted observation of stars not visible to the naked eye. Obtaining the data was a laborious process, particularly as visibility was best on clear winter nights when temperatures in the unroofed observatory room fell far below freezing. In addition to systematically cataloging stars, Flamsteed charted paths of the Moon and planets, obtained data on the precession of equinoxes, and made observations on the comets Halley’s comet[Halleys comet] of 1680 and 1681 that enabled him to correctly deduce that the two comets were actually one celestial body orbiting around the Sun. Flamsteed’s figures allowed Edmond Halley to calculate the comet’s orbit and predict the periodic return of the comet that bears Halley’s name.

Contemporaries questioned Flamsteed’s discovery of stellar parallax, but his assertions were subsequently vindicated. Theoretical astronomers argued that if the Earth did indeed revolve around the Sun, and the stars were positioned at varying (albeit vast) distances from Earth, the brightest stars should appear to shift position relative to the fainter and more distant ones when viewed from opposite sides of the Earth’s orbit. The apparent absence of this shift led Brahe to conclude that the Earth did not revolve around the Sun, and led Sir Isaac Newton to conclude that apparent brightness of stars was not a function of distance. Flamsteed believed he had detected a shift due to parallax in the position of Sirius, and that this provided conclusive evidence that the Earth orbited the Sun. To counter critics who faulted the optics of his telescope, he made similar observations on candles shining through pinholes, showing that he could indeed measure a small parallax involving a faint light source.

Flamsteed’s meticulous observations on the Moon’s Moon (of Earth) orbit Lunar orbit were sought by Newton, Newton, Sir Isaac Newton, Sir Isaac;gravitational theory who needed the data to check calculations based on his own gravitational theory. Newton was then working on the three-body problem, trying to characterize mathematically the complex trajectory of an object acted upon by two distinct gravitational sources. At first, Flamsteed supplied his figures freely, but he became less candid after some of them appeared in print without acknowledgment and others that were only tentative appeared prematurely. A bitter conflict, known as the astronomy wars, developed between Flamsteed, Newton, and Halley, profoundly affecting the completion and publication of Flamsteed’s research.

In 1704, Flamsteed was compelled by Queen Anne [p]Anne, Queen and the Royal Society to produce his findings, but he did not believe that he had accumulated enough accurate measurements to produce a publishable catalog. Queen Anne’s consort, Prince George George, Prince (Denmark) of Denmark, agreed to underwrite the costs of publication. Unfortunately, the prince died before much had been accomplished, and the project fell under the direction of the Royal Society Royal Society, England of London, of which Newton was president. Frustrated with what he saw as Flamsteed’s obstructionism, Newton furnished Halley with a copy of Flamsteed’s rough notes, from which Halley produced an abbreviated version of Historia coelestis Britannica in 1712. Flamsteed was so outraged that upon a change of government following Queen Anne’s death in 1714, he obtained as many copies of the 1712 volume as he could find and burned them in public.

A celestial map including the constellations Andromeda, Perseus, and Triangulum, published in a 1776 edition of John Flamsteed’s star catalog.

(Library of Congress)

Flamsteed had nearly finished the first volume of the complete Historia coelestis Britannica at the time of his death in 1719. Upon his death, all of his papers, as well as the instruments he personally purchased or constructed for the Greenwich Observatory, passed to his wife and assistant, Margaret Flamsteed, and to his adopted niece’s husband. Under Margaret’s editorial direction Flamsteed’s former assistants, Joseph Crosthwait and Abraham Sharp, completed the task of preparing a monumental body of data for publication in the form their mentor envisioned, despite lack of pay after Margaret lost most of her modest fortune after the collapse of the South Sea Bubble in 1720.


John Flamsteed’s star catalog set a standard for comprehensiveness and accuracy that lasted for nearly a century. A compact French edition of the atlas became the standard mariner’s guide to the heavens. The catalog contained few innovations in theoretical astronomy, but it laid a foundation without which subsequent discoveries would not have been possible. It firmly established the importance of telescopic sights in mapping the heavens, and showed what could be accomplished with the equipment available in the early eighteenth century.

An accurate star chart and detailed accounts of the lunar orbit and eclipses of the moons of Jupiter proved to be of limited practical use in determining longitude at sea, because of the difficulty of making precise observations on a moving deck, with a hand-held sextant, under less than optimal atmospheric conditions. John Harrison’s Harrison, John invention (1735) of the chronometer Chronometers —a timepiece that remained accurate on long voyages—rendered shipboard calculation of longitude from the lunar orbit unnecessary. Calculations of longitude using the stars was used, however, for determining the longitude of land-based observatories, and these, in turn, served to recalibrate chronometers during long voyages.

Thus, the Royal Observatory, Greenwich, and Flamsteed’s labors failed in their original, limited aim, but while doing so opened the universe to a new generation of astronomers and established Greenwich as the zero, or prime, meridian, the center around which celestial navigation is organized.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Clark, David H. Newton’s Tyranny: The Suppressed Scientific Discoveries of Stephen Gray and John Flamsteed. New York: W. H. Freeman, 2000. A thorough account of Flamsteed’s discoveries and a discussion of the importance of practical astronomy.
  • citation-type="booksimple"

    xlink:type="simple">Cook, Alan. Edmond Halley: Charting the Heavens and the Seas. Oxford, England: Clarendon Press, 1998. A good description of astronomical instrumentation in the early eighteenth century. Also, this work examines the reasons for the insistence on accurate measurement.
  • citation-type="booksimple"

    xlink:type="simple">Richardson, Robert S. The Star Lovers. New York: Macmillan, 1967. Includes nonscholarly accounts of work of Tycho Brahe, Jeremiah Horrocks, and Edmond Halley.
  • citation-type="booksimple"

    xlink:type="simple">Wilmoth, Frances, ed. Flamsteed’s Stars: New Perspectives on the Life and Work of the First Astronomer Royal, 1646-1719. Suffolk, England: Boydell Press and the National Maritime Museum, 1997. A collection of conference papers, with a chapter on optics that is valuable for perspectives on the practical limitations of the equipment used in Flamsteed’s time.

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