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Inventory no. 45975 - Epact entry

Epact number: 54866


Dated 1595; French
Brass; 182 mm in diameter

Main text

Several features of this instrument suggest that it was not produced in a commercial workshop. The dividing and engraving, for example, are not of high quality and there are some mistakes, while the rete is rather crude. The absence of a swivel in the shackle is odd, as are two lugs to keep the latitude plate in place. Marking the latitude projections for particular places, in this case Paris and Lille, is also unusual, and suggests the influence of a particular individual who has designed the instrument for his own needs.

The religious content of the decoration and inscription indicate that the owner was a Jesuit, while the prominent inscription on the rule asserts that 'ICK TOEBEHOORE PHILIS DE DIN' ('I belong to Philis de Din'). It seems probable that a Jesuit with an interest in astronomy has decided to make his own astrolabe, a practice recommended in a number of textbooks of the period.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 45,975

Detailed text

Limb riveted to the back plate of the mater, shaped throne, shackle and suspension ring. The shackle does not incorporate a swivel joint.

The limb has an outer scale of hours, 0 to 12 twice, divided to 30 minutes, subdivided to 15 minutes with alternate hatching, numbered by 1 hour. Inner scale of degrees 90 to 0 to 90 to 0 to 90, divided to 10, subdivided to 5 and to 1 with alternate hatching, numbered by 10. Inside the mater is blank.

Simple rete for 13 stars, with no band for the Tropic of Capricorn. Ecliptic circle with abbreviated zodiacal names and symbols, each with scale of 30 degrees, divided to 10, subdivided to 5 and to 1, numbered by 10.

One latitude plate, engraved on one side 'A PARIS 48 . DEGRE', on the other 'A . LILLE . 51 . DEGRE'. Each projection has azimuths for every 10 degrees, numbered by 10, and almucantars every 5 degrees to 70, numbered by 5; unequal hour lines beneath the horizon, numbered by 1, meridian line (marked 'MERIDES' and 'SEPTIO' and the Paris plate / 'SEPTRI' on that for Lille), east-west line (marked on the side for Paris 'HORISON RECTVS'), horizon (marked 'HORIZON OBLIQVVS' on the Lille side, 'HORISON OBLIQVS' on that for Paris, crepuscular line marked 'LINEA AVRORAE', Tropic of Cancer (marked 'TROPIC CANCRI') and equator (marked 'EQVINOCTIALIS'). Towards the lower end of the meridian line is 'TROPICVS CAPCORNI [sic]' on the Lille side, and 'TROPIC CAPRICONI' on that for Paris. The Lille side has lines for the houses of heaven, numbered by 1. The plate has two lugs, top and bottom, one fitting a hole, the other a slot, in the limb of the mater.

The back has an outermost degree scale 90 to 0 to 90 to 0 to 90, divided to 10, subdivided to 5 and to 1 with alternate hatching, numbered by 10. Zodiacal scale with Latin names and symbols for the signs, each with a 30-degree scale, numbered by 10, using the same divisions as the degree scale. There is no calendar scale. The upper two quadrants of the central space have an unequal hour diagram, while the central circle of this is engraved with the sacred monogram of the Jesuits and a heart, with the circling inscription: 'SIT NOMEN DOMINI BENEDICTVM IN SECVLA SECVLORVM 1595'. The lower two quadrants have a double shadow square, with scales 0 to 12 to 0 to 12 to 0, divided to 3, subdivided to 1 with alternate hatching, numbered by 3, and marked 'VMBRA' / 'VMBRA RECTA' / 'VERSA'.

Counterchanged alidade with zodiacal scale and symbols for the signs, rule marked 'ICK TOEBEHOORE PHILIS DE DIN', screw and nut.

See R. T. Gunther, The Astrolabes of the World (2 vols., Oxford, 1932), vol. 2, pp. 359-61.

Jim Bennett

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