Inventory no. 49033 - Epact entry
Epact number: 31206
Astrolabe
Unsigned
circa 1260; Hispano-Moorish
Brass; 84 mm in diameter
Main text
Although the instrument is unsigned and the attribution of a date is uncertain, this astrolabe has been given the earliest date among the western astrolabes in the collection in Oxford and, like the other very early examples, has been identified as Hispano-Moorish, that is, deriving from the Moorish culture in Spain.
In decorating the rete the maker has used a simple but effective combination of circular apertures. For the bases of the star pointers these are variously used singly, in pairs or in triplets, and sometimes the triplet arrangement merges to form a trefoil. On two bands tying together the tropic of Capricorn, the equatorial band and the ecliptic, there are trefoil designs open on one side.
Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 49,033
Detailed text
The rim of the mater is riveted to the back plate, and has a scale of 60 parts, each subdivided into 3 parts. The inside of the mater has a latitude plate for 24 degrees. Shackle, with no extant suspension ring.
The rete has 21 named stars, the supports for the pointers pierces by one, two or three circles or a trefoil design. The ecliptic, with the sometimes abbreviated names of the zodiacal signs divided to 2 degrees, is supported by an east-west bar and four ties.
Four latitude plates, marked for latitudes 30 and 35°; 40 and 45°; 48 and 52°; 55 and 60°, with lines for every 5 degrees of altitude and 10 degrees of azimuth, circles for tropics and equator and lines for unequal hours.
The back has a zodiacal calendar (with the first point of Aires at 13 March), with the constellation names, each sign divided to 2 degrees, and the months named (sometimes abbreviated), each divided to 2 days. A double shadow square has each side divided to 6 parts, subdivided to 12, not numbered. A central circular table is unfinished.
There is a pin, counterchanged alidade (broken), each vane with two pinholes, and horse wedge.
Jim Bennett