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Inventory no. 36338 - Epact entry

Epact number: 85668

Astrolabe

Unsigned
Late 14th century ?; origin unknown
Brass; 115 mm in diameter

Main text

The design of the rete of this astrolabe includes a semi-quatrefoil, also called trefoil. Differing from the Hispano-Moorish style, instruments of this type were developed in medieval Europe from about 1260 until about 1360, when the 'Y' type of Gothic astrolabe became common.

On the inner side of the mater there is a roughly engraved coat-of-arms which has not been identified.



Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 36,338



Detailed text

The mater of the astrolabe consists of two riveted layers of brass, one for the plate and the other for the limb.

The limb itself is divided into 360° starting at the top, to 5° to 1°, numbered by 15°.

Suspension is by means of throne, shackle and ring, all plain and not decorated.

The inner part of the mater has a rough coat-of-arms and another shield, very badly and faintly engraved.

The rete includes a semi-quatrefoil (or trefoil) pattern, within the ecliptic circle. The 32 named star pointers are of the flambent type. The ecliptic is engraved with the abbreviated names of the zodiac signs, and each sign is divided into 5 parts.

The two plates are engraved with east-west and meridian line, both tropic and equator lines, almucantars every 5° (except for one face in which they are marked every 4°), azimuth and unequal hour lines. The plates are not numbered, but on one of the plates is very faintly scratched $47$ for the latitude.

The back of the mater has a graduation in 360°, divided into four quadrants of 90° to 5° and to 1°, numbered by 10° degrees, with 90° at the zenith. Further to the centre is a zodiac scale (the first point of Aries is on 12 March) with each sign divided to 10°, to 5° and to 1°, numbered from [0] to 30° with the 10th and 30th numbered except for Capricorn where also the 20th is numbered. Between the zodiac and the calendar scale are degree numberings every 10°, starting at the top and marked 50° to 180° to 60°. This appears to be a later addition. Further to the centre is a calendar scale with only the 10th and the last day of the month numbered, and the names of the months abbreviated. Next to the centre are, in the top half, unequal hour lines and, in the bottom half, is a double shadow square, neither of them numbered. Next to the circle of the calendar scale is faintly engraved a division in degrees numbered by 10°.

The alidade is counterchanged and has two notched sighting vanes with one hole each, and Gothic shaped ends.

The single arm rule is simple, the pin has a circular decoration and the wedge is simple.

Ilaria Meliconi

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