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拍品專文
One of only eight recorded medieval astrolabe quadrants, and the only in private hands in contemporary leather case. Based on the style of engraving a loose date of 14th century would be placed upon the instrument, however upon studying the calendrical scales on the reverse Elly Dekker (1993) determined a date of manufacture between 1291 and 1311. The only other astrolabe quadrant to retain its leather case is held at the Musées départementaux de la Seine-Maritime in Rouen; and it is plausible to suggest a place of manufacture in Southern France based on the origins of the quadrans novus in Montpellier.
The astrolabe quadrant was invented by Jacob ben Machir ibn Tibbon (ca.1236-1305), who studied medicine at Montpellier, and translated many scientific texts from Arabic into Hebrew. His own astronomical work was highly regarded by later Renaissance astronomers and indeed cited by both Copernicus and Kepler. His Quadrant of Israel was written between 1288 and 1293, describing this newly invented instrument, which when translated into Latin in 1299 was termed the quadrans novus in order to distinguish it from the earlier and simpler invention in c.1288 of the quadrans vetus.
The mathematical technique of folding the astrolabe projection is known from an earlier Islamic instrument, the almucantar quadrant which is designed for use on a specific latitude. Ibn Tibbon’s design, however, is universal, and incorporates features of the quadrans vetus to solve a plethora of problems of spherical astronomy as well as those of astrology.
The use of black and red colouring on this instrument helps to highlight the method of folding. XRF analysis has shown the pigments to be bone-black and a mixture of red lead with cinnabar – the only other quadrant to use this colouring is the example in Rouen. The source for the unknown stars is yet to be identified, whereas for the Rouen quadrant it is MS Ashmole 1522. A rich manuscript tradition of the description survives, but only eight instruments are recorded, of which only two are in private hands; this example being the earliest of the eight.
The astrolabe quadrant was invented by Jacob ben Machir ibn Tibbon (ca.1236-1305), who studied medicine at Montpellier, and translated many scientific texts from Arabic into Hebrew. His own astronomical work was highly regarded by later Renaissance astronomers and indeed cited by both Copernicus and Kepler. His Quadrant of Israel was written between 1288 and 1293, describing this newly invented instrument, which when translated into Latin in 1299 was termed the quadrans novus in order to distinguish it from the earlier and simpler invention in c.1288 of the quadrans vetus.
The mathematical technique of folding the astrolabe projection is known from an earlier Islamic instrument, the almucantar quadrant which is designed for use on a specific latitude. Ibn Tibbon’s design, however, is universal, and incorporates features of the quadrans vetus to solve a plethora of problems of spherical astronomy as well as those of astrology.
The use of black and red colouring on this instrument helps to highlight the method of folding. XRF analysis has shown the pigments to be bone-black and a mixture of red lead with cinnabar – the only other quadrant to use this colouring is the example in Rouen. The source for the unknown stars is yet to be identified, whereas for the Rouen quadrant it is MS Ashmole 1522. A rich manuscript tradition of the description survives, but only eight instruments are recorded, of which only two are in private hands; this example being the earliest of the eight.