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Dated 1326; English
Brass; 132 mm in diameter

The mater which is cut from a solid block is graduated clockwise 0? to 360?, numbered by 5? and divided to 1?. The inside is empty. The throne is crescent shaped and the shackle saddle shaped.

On the rete, with a distinctive Y inside the ecliptic, 33 stars are indicated as follows: 'Mirac', 'batnachaythos', 'Menkar', 'Augetenar', 'Aldeboran', 'alhayok', 'Rigil', 'elgeuze', 'alhabor', 'algomeyza', 'Markeb', 'alfard', 'Cor leon', 'edub', 'algorab', 'alchimek', 'benetnac', 'alramek', 'elfeca', 'Yed', 'alacrab', 'alhae', 'Taben', 'Wega', 'altair', 'delfin', 'aldigege', 'Cor corvi', 'aldera', 'Musida equi', 'Cenok', 'Hum{erus} equi', 'Skeder'. Ten of the star-pointers are zoomorphic (birds and the head of a dog), two are heads of human beings. The circumferential frame has a dragon's head and tail respectively at the ends. The ecliptic bears the usual Latin names of the zodiacal signs, each sign is divided to 30?, numbered by 6? and divided to 2?. On the reverse the markings for the ecliptic are laid out and partially numbered, some of the star pointers are sketched.

All five plates bear markings for the circles of the tropics and the equator. One of the plates is otherwise left empty. Plates 1a, 1b, 2a, 2b, 3a, 3b and 4a and 4b have markings for the almucantars every 5? (every 3? on 3a and b), numbered by 10? (by 6? on 3 a and b), markings for the unequal hours numbered 1 to 12, and the very unusual marking for the prime vertical (except on 4b), without markings for the astrological houses. They are laid out and labelled for the following latitudes ('Latitudo'): 1a) 32? 0' 'Jerlm' (Jerusalem); 1b) 35? 30', 'Babilonie'; 2a) 41? 50', 'Rome'; 2b) 44? 40', 'Motis pessulani' [Montpellier]; 3a) 48? 32', 'parisius'; 3b) 51? 50', 'Oxonie' [Oxford]; 4a) 66? 0', 'Tab{u}la sub polo zodiaci'; 4b) 'Tabula sub Equinoctiali'.

The back bears four altitude scales starting at the top clockwise 90? to 0?, 0? to 90?, 90? to 0?, 0? to 90?, numbered by 5? and divided to single degrees. The single degree scale is also used for the circular solar scale, anticlockwise starting at the right, marked with the usual Latin names of the signs of the zodiac. Each sign is divided to 30, numbered by 5?. Further to the inside is an eccentric calendrical scale, marked with the Latin names of the months (with the slightly unusual forms 'Marcius' and 'Mayus'), anticlockwise starting at the first point of Aries, the equinoxes correspond to March 13 and September 16. Inside this scale is a band with the names of 46 saints (amongst them on 19th May Dunstan, 26th May Augustine of Canterbury, 17th June Botulph) and Christian feasts linked to given dates and Dominical letters. The lower half of the vacant space is taken up by a pair of shadow scales to the base of 12, numbered by 2. Above the diameter between the shadow scales and the calendrical scales is the date '1326'.

The alidade is counter-changed and has two sighting vanes, the pin is very simple, the wedge is unusually long with a small horse head at one end.

The instrument was purchased in 1909 from van Duren and is described and illustrated in R. T. Gunther, The Astrolabes of the World (2 vols, Oxford, 1932), pp. 465-7, no. 291; F. A. B. Ward, A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum (London, 1981), pp. 112 ff., no. 325 (with plate LI).

Silke Ackermann

British Museum, London
Registration no. MLA 1909,6-17.1

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