(b. Broughton, England, June 1610; d. Broughton, July 1644 [?])
The son of John Crabtree, a Lancashire farmer of comfortable means, and the former Isabel Pendleton, Crabtree established himself as a successful clothier or merchant at Manchester and married Elizabeth Pendleton in 1633. His interest in astronomy led him to undertake a series of precise observations, only a small fraction of which were published some time after his death, and to maintain an active correspondence, most of it now lost, with Samuel Foster, professor of astronomy at Gresham College, London, and the young astronomers Jeremiah Horrocks, William Gascoigne, and Christopher Towneley.
Crabtree’s observations convinced him that, despite their errors, Kepler’s Rudolphine Tables were the best extant; and he became one of the earliest converts to Kepler’s new astronomy, accepting the latter’s elliptical orbits and concurring in his call for the creation of a celestial physics. By 1637, within a year after they began to correspond, Crabtree convinced Horrocks of the superiority of the Keplerian system over those employing circular components. Both men made many corrections in Kepler’s tables, bringing them into better agreement with observation; and Crabtree converted them to decimal form.
As a result of these revisions, Horrocks was able to predict and observe the transit of Venus of 4 December 1639, the first such observation ever made. Having been notified by Horrocks about a month before of the impending transit, Crabtree was the only other astronomer to observe it. Although he failed to record his data as precisely as Horrocks, their general observations were in agreement; and Horrocks obtained improved figures for the diameter of Venus, the elements of its orbit, and the distance of the earth from the sun. Although a capable astronomer in his own right, Crabtree is remembered chiefly for his influence on and relationship to Horrocks.
I. Original Works. Some of Crabtree’s observations were published in Horrocks’ Opera posthuma, John Wallis, ed. (London, 1672, 1673, 1678), pp. 405–439; and John Flamsteed, Historia coelestis Britannicae (London, 1725), 1, 4. Extracts from his letters to Gascoigne are printed in William Derham, “Observations Upon the Spots… Upon the Sun,” in Philosophical Transactions of the Royal Society, 27 (1711), 280–290; and “Extracts From Mr. Gascoigne’s and Mr. Crabtrie’s Letters,” ibid., 30 (1717), 603–610.
II. Secondary Literature. Horrocks, Opera posthuma, pp. 347-338 has extracts of Horrocks’ letters to Crabtree. See also Horrocks’ The Transit of Venus Across the Sun, trans. with “A Memoir of His Life and Labours” by Arundell B. Whatton (London, 1859), passing; and John E. Bailey, “Jeremiah Horrox and William Crabtree, Observers of the Transit of Venus, 24 Nov., 1639,” in Palatine Notebook, 2 (1882), 253–266.
Architectural Review, lxxxv (June 1939), 291–8; and clxxxvii/1115 (Jan. 1990), 75–9