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Instrument type

circa 1260; Hispano-Moorish
Brass and copper; 178 mm in diameter

The mater consists of two soldered layers of brass, one constituting the plate and the other the rim and the throne.

The limb is engraved with a scale of degrees, from [0] to 360? by 5?, divided to 1?, numbered by 5? with 0? at the zenith.

The inside of the mater is engraved with the lines of the equator and Tropic of Cancer.

Suspension is by throne, shackle and ring. The throne is filleted all around the side.

The rete is of Gothic type with 18 stars, 17 of which are named. The star pointers are dagger-shaped. The ecliptic has engraved the names of the zodiac signs and presents faint divisions on the edge. The east-west bar is counterchanged on each side. The ecliptic and Capricorn band are connected by eight bars, one of which is counterchanged twice on each side, and the other two present a globular decoration on the side. The equatorial line is connected by another bar to the Capricorn band, which is divided into divisions of 5?. There is no meridian bar.

The five copper plates are all engraved with east-west and meridian line, tropic and equator lines (except for the back of the first plate).

The plates are engraved for latitudes according to the Ptolemaic climates.

Plate 1a is engraved for 'CLIA I LAT 12', and has almucantars engraved every 12?, as well as azimuth lines and hour lines but neither is numbered. Plate 1b has almucantars engraved every 6? but no line for the Tropic of Cancer. None of the lines is numbered.

Plate 2 is engraved with almucantars engraved every 12?, for 'CLIA 2 LAT 24' on one side and 'CLIA 3 LAT 30' on the other.

Plate 3 is for 'CLIA 4 LAT 36' and 'CLIA 5 LAT 41', and on both sides has almucantars every 6?, azimuth lines and a twilight line, none of which is numbered. The unequal hour lines are numbered from I to 12.

Plate 4 has almucantars every 6? and hour lines numbered from 1 to 12. On one side is for 'CLIA 6 LAT 45' and has azimuth lines engraved, and on the back is for 'CLIA 7 LAT 48 [?]' with no azimuth lines.

Plate 5 has only east-west and meridian line, tropics and equator line engraved.

The back of the astrolabe has a scale of degrees divided in four quadrants of 90? by 5? subdivided by 1?, numbered by 5?, with 90? at the poles, and a zodiac scale with every sign named and divided from [0?] to 30? by 5?, also numbered by 5?. On a more inner circle is a calendar scale with only the division in months and a sketch of a double shadow square and numbering. The spelling 'MADIVS' is unusual.

The single arm rule is simple and not decorated, the alidade is counterchanged (one sight is missing) and has Gothic ends, and the wedge is horse-shaped. The pin is decorated.

See R. T. Gunther, The Astrolabes of the World (2 vols, Oxford, 1932), vol. 2, p. 316.

Ilaria Meliconi

Museum of the History of Science, Oxford
Inventory number 43504

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