Hevelius, Johannes

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Hevelius, Johannes

(b. Danzig [now Gdańsk], Poland, 28 January 1611; d. Danzig, 28 January 1687)

astronomy, instrument making.

Hevelius (also known as Heweliusza, Hevel, or Hewelcke) was one of at least ten children of a prosperous brewer and property owner. Between 1618 and 1624 he was educated at a Gymnasium in Danzig; and when it was closed, he was sent to a school near Bromberg (Bydgoszcz), Poland, to acquire fluency in Polish. In 1627 he returned to the Danzig Gymnasium, where he came under the influence of Peter Krüger, a teacher of mathematics and astronomy. Krüger not only took him through the usual curriculum but also gave him private lessons in astronomy and saw to it that he learned the practical arts of instrument making and engraving.

In 1630 Hevelius went to study jurisprudence at the University of Leiden; during the voyage he made observations of a solar eclipse which he subsequently published in the Philosophical Transactions of the Royal Society. Besides his legal studies he acquired a further smattering of mathematics and its applications to mechanics and optics before leaving for London in 1631. From 1632 to 1634 he visited Paris, calling on Gassendi and Boulliau, and Avignon, calling on Athanasius Kircher. His letters to Krüger from this period survive. For two years he worked in his father’s brewery, while studying the constitution of Danzig with a view to entering public service. In 1635 Hevelius married Katharina Rebeschke, daughter of a wealthy citizen of Danzig, and at first appears to have had little inducement to pursue his astronomical studies, despite Krüger’s pleas. He observed the solar eclipse of 1 June 1639; and this year, in which he began systematic astronomical observations and which also saw the death of Krüger, was a turning point in his career.

Hevelius undertook three laborious tasks: constructing his own astronomical instruments, corresponding with many foreign astronomers, and holding civic office, first as honorary magistrate (1641) and later (1651) as city councillor (Rathsherr). Although his father’s death in 1649 meant a further claim on his time for the day-to-day running of the brewery, it provided him with funds to build what became, for a short period, the world’s leading astronomical observatory. Hevelius’ first observatory was a small upper room; in 1644 he added a small roofed tower to his house and later erected a platform with two observation houses, one of which could be rotated. In 1663, the year following the death of his first wife, he married Catherina Elisabetha Koopman, his junior by thirty-six years; their three daughters lived to maturity. The daughter of a rich merchant and unusually well-educated, his second wife played a considerable part in the running of the observatory. In two plates of Machina coelestis, Elisabetha is represented assisting her husband in his observatory. She acted as hostess to many visiting astronomers—Halley being perhaps the best-known—and after her husband’s death she edited many of his unpublished writings.

Hevelius suffered a considerable tragedy in September 1679 when, during his absence in the country, a fire destroyed his Danzig house and observatory, his instruments and the workshop for their manufacture, most of his books and papers, and his printing press. This entailed far more than a heavy financial blow, but Hevelius began to repair the damage at once, apparently having received financial help from many quarters. By August 1681 the observatory was rebuilt and reequipped, although with fewer instruments and these inferior to the ones that had been destroyed. The list of items saved is of some interest and includes most of the bound copies of his books, many of his most valuable manuscripts—including his catalogue of fixed stars, his Globus coelestis correctus et reformatus (which was in press), and Prodromus astronomiae (also approaching publication)—thirteen volumes of correspondence, and all of Kepler’s manuscripts. Other works rescued were those subsequently published as Annus climactericus (1685) and Firmamentum Sobiescianum sine Uranographia (1690). There is a description of the fire in the preface to the Annus. Hevelius survived this catastrophe by more than seven years; but his health suffered from the shock and was not improved by a controversy with Hooke, into which he had been drawn several years earlier. He died on his seventy-sixth birthday.

Hevelius was such a punctilious publisher of his own achievements that his chief publications give a reasonably complete picture of his work. The first important work published by Hevelius was his Selenographia: Sive lunae descriptio; atque accurata, tam macularum eius quam motuum diversorum, aliarumque omnium vicissitudinum, phasiumque, telescopii ope deprehensarum, delineatio, etc. (1647). After a fine portrait of the author and a number of extravagantly laudatory verses by friends, Hevelius describes and illustrates an optical lathe for turning telescope lenses and gives methods for judging the parameters and qualities of lenses. His authorities are typical of the day: Witelo, Kepler, Scheiner, and Maurolico, among others. He describes Scheiner’s helioscope (which he was later to modify), the microscope, and the polemoscope (the military periscope). One of his astronomical telescopes, about six feet long, is shown well-mounted mechanically—with massive ball-joints as accessories—but not equatorially. It is fitted with only a rudimentary quadrant for altitude and has no azimuth scale. Another device used with the telescope is a right-angled eyepiece for observing near the zenith. Hevelius was in the habit of using card stops with his instrument, and by their use he claimed to have perceived stars with a finite disk—a spurious appearance, of course. The largest telescope mentioned was twelve (Danzig) feet long and of approximately 50X magnification. (All lengths quoted subsequently are in units of a Danzig foot, equivalent to approximately eleven inches.)

Hevelius recounted his observations of the planets, especially Saturn, drawing it as a globe with two crescent-like handles. He recorded movements of the satellites of Jupiter, their configurations, eclipses, latitudes, and periods of revolution. He also made sunspot and eclipse observations with the helioscope, which was illustrated in both the Selenographia (plate L) and the Machina coelestis (using the same plate, now lettered “V”). A telescope pierced the center of a ball within a socket which was mounted on the wall of a darkened chamber, so that an image of the sun could be projected on blue paper pinned to a movable easel. Certain modifications of this, his first helioscope, were announced in the later book, in which they were said to have been found in 1661 by consultation with Bullialdus (Boulliau), “then one of my most valued friends.” The problem of keeping the sun’s disk at the same place on the easel, for protracted observation, was solved in a way of which Hevelius was inordinately proud, although it was very inelegant by comparison with the equatorial mounting known in other connections long before. An assistant controlled two screws which determined the slope of a table across which the easel moved. The method was somewhat simplified with the help of a table of the angles between the ecliptic and the vertical which Hevelius calculated for different solar longitudes and times. He might have found the more satisfactory method had he not followed Scheiner’s example so closely.

The Selenographia proper begins with arguments disproving the ancient idea that the moon is a mirror reflecting the earth; but with the eighth chapter its contents become memorable. There Hevelius delineates and discusses the lunar markings and the movement of libration. The first lunar maps had been drawn by Thomas Harriot and Galileo almost as soon as telescopic means were available to them. Matthias Hirzgarter, in Detectio diopirica corporum planetarum verorum (Frankfurt, 1643), was the first to publish a map, although an indifferent one, of the complete hemisphere. Hevelius was obliged to rely on his own observations; and the excellent engravings of Selenographia which resulted, done by his own hand, were judged worthy of reproduction by the fastidious Riccioli in his Almagestum novum (Bologna, 1651).

Hevelius gave many new names to the lunar mountains, craters, and other formations; most of them are still used. His most profitable task, though, was to draw the moon in different states of libration. He was incapable of either accounting for the multiple causes of the phenomenon or of satisfactorily formulating empirical laws to account for it; nor, a fortiori, did he know of the complex terrestrial and lunar motions responsible for them. Hevelius’ descriptions of a librational cycle of shadow changes in the lunar details, his method of judging the libration by means of changes in the apparent (telescopic) separation of a pair of lunar details, and his introduction of rudimentary lunar coordinate systems provided a sound basis for the work of subsequent astronomers. Selenographia ends, aside from appendixes of various observations, with a description of a mounted lunar globe, perhaps the first of its kind, permitting the representation of librational movements. One of the conclusions of the appendixes is that the mean synodical period of solar rotation, judged from sunspot movement, is twenty-seven days. Hevelius did not, of course, appreciate the change of velocity with distance from the solar equator.

The second great work by Hevelius, not published until more than twenty years after the Selenographia, was Cometographia, totam naturam cometarum, ut pole sedem, parallaxes, distantias ortum et interitum, capitum, caudarumque diversas facies... beneficio unius eiusque fixae et convenientis hypotheseos exhibens, etc. (1668). An introductory engraving is doubly interesting; it depicts Hevelius sitting at a table with a cometary orbit shown as a conic section combined with a spiral, the sun at the focus of the former. By contrast, a figure of Aristotle holds an illustration of some linear and sublunary cometary paths. Below is a valuable illustration of Hevelius’ house and observation platform.

Helevius devoted the first book of the Cometographia to the comet of 1652, showing, for example, that its parallax was not great enough for it to be sublunary. In fact he had an ingenious but inaccurate way of judging parallax and greatly underestimated the comet’s distance. Later Hevelius wrote on the physical constitution of comets, but without much insight—favoring, for instance, a disklike (as opposed to a spherical) structure for the head. In books VI, VII, and XII he collected a considerable body of information, especially concerning the comets of the two preceding centuries. He supposed comets to be condensed planetary exhalations, and he believed them linked with the material responsible for sunspots, thus leading himself into obvious difficulties over velocities and orbital planes. When he questioned the physical causes of cometary motions he was barely able to pass beyond a vague and qualitative explanation in terms of impulses provided by interacting exhalations. It was by analogy with the parabolic motion of terrestrial projectiles that he decided on a fundamentally parabolic motion for comets. When in due course the idea was accepted, it was not as a result of the hypothesis of Cometographia; and those who have claimed priority for Hevelius are on very weak ground.

One of Hevelius’ first efforts as an engraver is the frontispiece to Kircher’s Primitiae gnomonicae catoptricae (Avignon, 1635), described by T. Przypkowski as “the richest known diagram of a reflexive sundial”; and the competence of its engraver may be explained by the great interest of Hevelius’ first teacher, Peter Krüger, in gnomonics. In 1638 Hevelius designed a new type of dial, several examples of which he is thought to have made. The signed original disappeared in 1945. A fine dial by him, but of a totally different sort, is a triple mural dial on the wall of the royal palace of Wilanów, built near Warsaw for the Polish king Jan III Sobieski about 1680. In Hevelius’ library were forty items on gnomonics, omitting nothing of importance published on the subject.

Hevelius undoubtedly owed the success of his observations to his skill in designing, making, and engraving instruments; and the work in which he described his techniques was of very great interest to his contemporaries. Machina coelestis, pars prior, organographiam, sive instrumentorum omnium quibus auctor hactenus sidera rimatus ac dimensus est...; item de maximorum tubor constructione et commodissima directione, etc. (1679); fewer than 100 copies survived the fire.

One of Hevelius’ first efforts at making large instruments was to complete a copper azimuth quadrant which Krüger had begun, the expense of which was to be met by the Danzig senate. He went on to copy several of Tycho’s instruments. That he had made a wide study of earlier instruments is evident from the first book of Machina coelestis, in which he evaluates the accuracy of the observations of ancient and modern astronomers. Subsequent descriptions of his instruments include the following (all in the first volume of Machina coelestis): copper quadrant of radius three feet, wooden base with four screw feet (chap. 2); copper sextant of radius three feet, for two observers (chap. 3); copper sextant of radius four feet for a single observer (chap. 4); wooden quadrant with stand and counterpoise (chap. 5); wooden sextant of more than six feet radius, after Tycho’s design (chap. 6); wooden double octant of radius eight feet, with two centers and two scales, having no alidade but movable pinnules (chap. 7); three copper quadrants of between one and two feet radius, each equipped with verniers (with thirty-one divisions, against thirty) equipped with screws for fine adjustment (Chap. 8); a very fine large quadrant of five feet (for altitude) and of four feet (for azimuth), with counterpoises, pulleys, ropes, and screws for adjustment, the pinnules with two pairs of slots at right angles, all housed in an octagonal building (chap. 9); large copper vernier (with sixty-one divisions, against sixty) quadrant with mercury level, all so well counterpoised that “the slightest breath of air would cause it to turn,” although it weighed 800 (Danzig) pounds (chap. 10); large brass sextant cross-membered in iron to prevent flexing, and of more than six feet radius, again very finely counterpoised with weights, ropes, and pulleys (chap. 11); copper quadrant of radius nine feet, but with scale filling only an octant, cross-membered in iron, being for use by two observers, and engraved with portraits of Hipparchus, Ptolemy, Copernicus, and Tycho (chap. 12); and portable sextant (chap. 13).

The first volume continues with a discussion in great detail of the design of pinnules, the division of instrument scales, the establishment of the meridian (and magnetic variation), and horological matters. But those chapters which were perhaps most widely read at the time (18–24) concerned his telescopes, their housings, and their mountings. Hevelius had been spurred on to build new telescopes after hearing of the discoveries (including that of the Orion nebula in 1656) made by Christian Huygens. Both men were convinced of the advantages of long-focus objectives: small chromatic and spherical aberration and high magnification with a given eyepiece, although image brightness was reduced for an extended object. Hevelius carefully described his instruments with focal lengths of 30, 40, 50, 60, 70, 140, and 150 feet (chap. 20). The problems of mounting were immense. From round tubes and tubes of box sections, he finally reduced the weight of his tube by leaving it in an open structure of narrow wooden spars, with circular rings at intervals acting as spacers (and blackened as optical stops). The larger telescopes were slung from tall masts (one of ninety feet is mentioned), and movement was effected by assistants with numerous guy ropes and pulleys. The largest seems to have had a lens about eight inches in diameter and was therefore of approximate focal ratio 1:225.

The flexing of the open frame—especially in a wind—presented the greatest mechanical problem, for the view of the objective could be almost totally obscured by the stops. Hevelius tried to solve this problem by running ropes of adjustable tension along the length of the telescope, but Halley (who sent him lenses from England) informs us that this was to no avail and that the largest telescope was useless. Problems of housing and storage were more easily solved by a prince than by a man of small means; and counting himself in the latter category, Hevelius described appropriate economies such as he had made at Sternenburg—as he called his observatory. He was often completely misled by optical imperfections, spending, for instance, much time with a micrometer measuring the diameters of spurious stellar disks. (His adaptation of Huygens’ micrometer was used to better purpose for planetary diameters.)

Halley, who had first written to Hevelius as an undergraduate in 1674, visited Danzig in 1679 at the instigation of the Royal Society, in the hope of resolving amicably a violent controversy begun by Robert Hooke. Hevelius had sent copies of his Cometographia to several fellows of the Society, including Hooke, who had in return recommended the use of telescopic rather than plain sights on graduated instruments. The correspondence continued, with neither party yielding ground; and in reply to the Machina coelestis, Hooke had written his Animadversions on the First Part of the Machina Coelestis of...Hevelius (1674). There are too many imponderables for us to pronounce on the merits of the several arguments, but clearly the Danzig arguments ceased to apply as the mechanics and graduation of instruments steadily improved.

The second volume of the Machina coelestis contained a considerable collection of observational data and reductions of almost every sort—a mine of information, although rare, for later astronomers—but not distinguished by its organization or by any new findings of importance. As may be judged from the earlier list of instruments, he generally observed—as was then customary—the angular separations of objects; the volume contains more than 20,000 such measurements, 7,000 relating to the fixed stars. By 1685 he had prepared another large volume of observations, Annus Climactericus, dealing principally with planets and comets. By far the most widely known of his compendia of observations, however, was published after his death by his wife: Prodromus astronomiae exhibens fundamenta quae tam ad novum plane et correctionem stellarum fixarum catalogum construendum quam ad omnium planetarum tabulas corrigendas omnimode spectant etc. (1690). It is a catalogue of 1,564 stars arranged alphabetically under constellation names and by stellar magnitude within constellations. Latitude, longitude, right ascension, and declination are given (the latter pair of coordinates being often miscalculated even though two assistants were employed to verify calculations). John Flamsteed, another of Hevelius’ many correspondents, was later to reprint the catalogue, with a different arrangement, in volume III of his Historia coelestis Britannica (1725). Hevelius named eleven new constellations formed of stars not included in earlier groupings; seven of these names are still used.

An idea of Hevelius’ relative accuracy may be had from a comparison of the separations of ten randomly chosen bright stars: Tycho’s r.m.s. error is of the order of 1’40″, Hevelius’ of 50″, and Flamsteed’s (with telescopic aid) of 40″. Atmospheric refraction was an important and variable source of error in all these cases.

The Prodromus continued a tradition of reprinting earlier catalogues, not only of William IV, landgrave of Hesse, Riccioli, Tycho, and Ptolemy. but also of Ulugh Beg’s Samarkand observatory. Illustrating the constellations of Hevelius’ catalogue was a volume of fifty-six plates, possibly engraved in part by Hevelius himself: Firmamentum Sobiescianum, sive Uranographia (1690). Contemporary globes, such as those by G. C. Eimmart, and Gerhard and Leonhard Valk, often acknowledge Hevelius as their source. Later constellation outlines and draftsmanship also owed much to Uranographia.

If to Hevelius’ correspondence with astronomers throughout Europe we add his published writings not mentioned above, we may form some idea of his formidable industry. He does not belong to the highest rank of theoretical astronomers, although he was the doyen of mid-seventeenth-century astronomers. His character might well be judged from the sentiments expressed on his engraved title pages, two of which stand out: “Not by words but by deeds” and “I prefer the unaided eye.”


I. Original Works. Reasonably full titles of Hevelius’ principal books have been given in the text. They are included with a number of lesser works, all in short-title form, in the following list; the place of publication is invariably Danzig: Selenographia (1647); Excellentissimo... Eichstadio eclipsis solis observata (1650); Illustribus viris... Gassendo et Is. Bullialdo (1652); Epistolac (1654); Dissertatio de nativa Saturni facie (1656); Mercurius in sole visus (1662); Cometographia (1668); Epistola ad Oldenburgium de cometa (1672); Machina coelestis, 2 pts. (1673–1679); Excerpia ex literis... ad Hevelium (1683); Annus climatericus (1685); Uranographia (1690); and Prodromus astronomiae (1690). The posthumous works were often bound together. Several of the above works are available in modern facsimile editions.

For further bibliography see Allgemeine deutsche Biographie, XII (1880), 341–343; D. Wierzbickiego (see below); and especially L. C. Béziat, “La vie et les travaux de Jean Hévélius,” in Bullettino di bibliografia e di storia delle scienze matematiche e fisiche, 8 (1875), 497–558, 589–669, also published separately (Rome, 1876).

Hevelius left correspondence and observations filling more than seventeen folio vols., sold nearly forty years after his death by his son-in-law to Joseph-Nicholas Delisle for 1,200 ducats. (Delisle had been called to Russia by Catherine I and was visiting Danzig en route.) See Bibliothèque de la Chambre des Députés, MS 1507, I, 36. This material passed first to the Bureau des Longitudes, Paris, and thence to the Bibliothèque Nationale and the observatory, where fifteen vols. remain. They are available on microfilm. Hevelius was responsible for preserving many of Kepler’s papers, which also passed to his heirs and ultimately to Leningrad. The catalogue of Hevelius’ library is in the Paris observatory, MS C, 2, 5.

II. Secondary Literature L. C. Béziat (see above) is a fundamental source. See also A. von Brunn, “Johannes Hevelius’ wissenschaftliche Tätigkeit...,” in Schriften der Naturforschenden Gesellschaft in Danzig, n.s. 13 (1911), 30-44: G. A. Seidemann, Johannes Hevelius (Zittau, 1864); and J. H. Westphal, Leben, Studien und Schriften des Astronomen J. Hevelius (Königsberg, 1820). A very good memoir in Polish is D. Wierzbickiego, “Źywot i dzialalność Jana Heweliusza, astronoma polskiego.” in Pamiętnik Akademii umiejętności w Krakowie, Wydzialy: Filologiczny i Historyczno-Filozoficzny, 7 (1889), 22–78. Useful for personal detail and relations with Halley are E. F. MacPike, Hevelius, Flamsteed and Halley (London, 1837), pp. 1–16, 75–124;and Correspondence and Papers of Edmond Halley (Oxford, 1932), passim. For fuller details of Hevelius’ instruments, see E. Zinner, Deutsche und niederländische astronomische Instrumente des 11.–18, Jahrhunderts, 2nd ed. (Munich, 1967), pp. 375–382. See also Tadeusz Przypkowski, “Gnomonics of John Hevelius,” in Actes du dixiéme congrès international d’histoire des sciences, II (Paris, 1964), 695–697. The best comparative ed. of the star catalogues of Hevelius and others is Francis Baily, Memoirs of the Royal Astronomical Society, vol. 13 (1843), 296 pp. including prefaces and notes. For a facs. of Uranographia, with intro. especially concerning Ulugh Beg’s observatory, see Jan Hevelius, Yulduzlar osmonining atlasi, V. P. Shcheglov, ed. (Tashkent, 1968). The place of Hevelius’ telescope in the history of that instrument is discussed in H. C. King, The History of the Telescope (London, 1955). Still perhaps the best account of the contents of Hevelius’ principal works is J. L. Delambre, Histoire de l’astronomie moderne, II (Paris, 1821), 435–495. For an example of the influence of Selenographia, see W. H. Ryan, “John Rusell, R. A., and Early Lunar Mapping,” in Smithsonian Journal of History, 1 (1966), 27–48.

J. D. North

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