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Instrument type

Later 15th century ?; Italian
Brass; 59 mm in diameter

There is no raised limb, the 'mater' being simply a flat plate with a degree scale 90 to 0 to 90 to 0 to 90, divided to 10, subdivided to 2, numbered by 10. Three-lobe throne (no shackle or ring). The central area of the plate is engraved with almucantars on both sides of the horizon, and with unequal hour lines on the lower part of the plate. Some crudely engraved lines have been added later.

The rete has a short index and four star pointers with trefoil of fleur-de-lis heads. A broad arc spanning one diameter of the rete has the abbreviated names of the zodiacal signs and an unnumbered scale. The rete is held in place by a rivet and there are do separate plates.

The back has a degree scale similar to the front, and two quadrants of the remaining space are occupied by an unequal hour diagram and a double shadow square with scales 0 to 12 to 0 to 12 to 0, divided to 3, subdivided to 1, numbered by 3. Alidade with pinhole sights.

See R. T. Gunther, The Astrolabes of the World (2 vols, Oxford, 1932), vol. 2, pp. 319-20.

Jim Bennett

Museum of the History of Science, Oxford
Inventory number 40829

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