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Inventory no. 37878 - Epact entry

Epact number: 28895

Astrolabe

Unsigned
circa 1260; Hispano-Moorish
Brass; 145 mm in diameter

Main text

This astrolabe presents typical Moorish features such as the rectangular mounts for the four star pointers on the top of the rete. Nonetheless, the engraving is partly in very bold Lombardic script, though also in a distinct lighter script.

The rete and a plate for the latitude of Paris are engraved with this latter script, so it is possible that the instrument had been adapted, the rete re-engraved and one of the plates made (or re-engraved) for a later French owner.



Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 37,878



Detailed text

The mater of this astrolabe is made of three riveted layers of brass, the central of which is cast in one piece with the throne.

The limb is engraved with two scales, one for hours, divided from 1 to 12 twice with a faint division of each hour in 15 parts, the other divided in degrees from [0] to 360° (at the zenith) by 1°, numbered by 10°. The part of the limb between 100° and 110° has been replaced.

Suspension is by ring, shackle, swivel and a three-lobed throne with a simple decoration.

The rete is of Gothic type with 27 named stars, and is etched with a different, perhaps later, script. The ecliptic is engraved with the names of the zodiac signs, divided by 2°, numbered from 10° to 30° by 10°, and is connected to the Capricorn band with two ties. The east-west bar is counterchanged twice on each side and decorated. The bar has been patched. The equinoctial band is interrupted by two cusped Gothic arches. The star pointers are flame shaped with perforated bulbar bases, except for four of them which are carried on rectangular mounts on the ecliptic.

There are seven plates with engraved east-west and meridian lines, both tropic lines and equator, and all, except for plates 1b and 6b, have unequal hour lines numbered from I to XII. In all plates except 1b, 2b and 6b the almucantars are engraved every 6°.

Plate 1a is inscribed on one side 'Latitudo XXXVIII' and the almucantars are not numbered. Plate 1b is etched more faintly and in the same script as the rete 'Parisius' with a scroll decoration. The almucantars are engraved every 3° but not numbered and the hour lines are marked in full 'Prima', 'Secunda' ... 'Duodecima'.

Plate 2a is inscribed 'Cesar augusta [Saragoza] latitudo |X|I' [41] and plate 2b is engraved for 'Latitudo |X|II' [42]. On both sides the almucantars are engraved every 3° and numbered from VIIII to L|X| by nine.

Plate 3a is engraved for 'Latitudo |X|V' [45] with almucantars numbered from XII to L|X| [90] by nine. Plate 3b is engraved for 'Latitudo |X|V' [45] with almucantars numbered XII to L|X| [90] by 12.

Plate 4a is engraved for 'Latitudo |X|VII' [47] with almucantars numbered from XII to L|X| [90] by 12. Plate 4b is engraved for 'Latitudo |X|VIII' [48] with almucantars numbered from VIIII to L|X| [90] by nine.

Plate 5a is engraved for 'Latitudo |X|IX' [49] with almucantars numbered from XII to L|X| [90] by 12. Plate 5b is engraved for 'Latitudo |X|X' [50] with almucantars numbered from XII [other II deleted] to L|X| [90] by 12.

Plate 6a is engraved for 'Latitudo LV' with almucantars numbered from XII to L|X| [90] by 12. Plate 6b is engraved with 'Latitudo ad Parisius' in the same script as the rete and the unequal hour lines are indicated in Arabic numerals 1 to 12. These numerals are engraved next to the limb of the plate and are repeated next to the tropic of cancer line. The engraving is very faint, and the almucantars are engraved every 3° but are not numbered.

Plate 7 is engraved for 'Latitudo LVII' and 'Latitudo LVIII' with almucantars numbered from XII to L|X| [90] by 12 on both sides.

The back of the mater has a zodiac scale with each sign named in abbreviated form, divided by 5°, subdivided by 1° and numbered from 10° to 30° by 10°. On an inner circle is a calendar scale with the months named (abbreviated) divided to the day, with the 10th, 20th and last day numbered. The first point of Aries corresponds to the 19th of March. On the top half are unequal hour lines numbered 1 to 6, and on the bottom half is a double shadow square indicating 'umbra recta' and 'umbra versa' divided to |1/2| and numbered by 4.

The diametrical rule is counterchanged and decorated with arabesques, and is marked on one side '20', '30', '45' (?), '70'(?), '90'.

The alidade is counterchanged twice with Gothic ends, and the two sights have double holes.

The wedge is horse-shaped and the pin is decorated with concentric circles.

See R. T. Gunther, The Astrolabes of the World (2 vols, Oxford, 1932), vol. 2, p. 340.

Ilaria Meliconi

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