The astrolabe reached its technical peak between the XIth and XIVth centuries and special mention should be made of the Arab craftsmen from the Muslim west for their engraving and mathematical ability. Two schools can be singled out. One was represented by Abu Bekr b. Yusuf (fl.1208-1318) from Marrakesh, who produced instruments large and small, but very accurate. The other was that of Muhammad b. Futtuh (al-Khama ‘iri, fl.1207-1236) from Seville, which included Ibn Baso the Elder and his son Ahmad b. Husayn b. Baso (?-1309), who worked in Granada, in the south of Spain, at the end of the XIIIth and beginning of the XIVth century.
After careful analysis by the astrolabe experts Almerico da Schio and Marcel Destombes (see op. cit.), the astrolabe of Bologna was attributed to the second school and, in particular, to Ibn Baso the Elder, muwwaqit, i.e. time calculator, at the great mosque of Granada, designer of solar quadrants and other instruments and author of a treatise on the astrolabe written in the year 673 of the Hegira (1274 AD). The type of engraving and the "Magreb kufic" characters used, along with the date of the vernal equinox recorded on the back, all suggest a dating of around 1280. If the attribution is correct, it is the only example of this craftsman’s work that has come down to us.
The rete has four silver nails over the two orthogonal diameters and twenty-nine stars, the maximum that can be found in astrolabes of this size.
There are seven plates inside the mater, all made for latitudes corresponding to localities on the coast of West Africa and the south of Spain, except one that refers to the holy cities, Mecca and Medina, and another that is written in Latin and refers to the north of Italy. This latter plate, undoubtedly of later origin - probably of the XVth century - suggests that this astrolabe, built for a Spanish Arab of the XIIIth century, somehow fell into the hands of an Italian scholar who, in order to be able to use it, had a plate suited to his latitudes engraved.
Original plates (c.1280):
"This astrolabe belonged to Dr. Luciano Toschi who bequeathed it to Dr. Orso Sassi, both from Imola; Sassi, who died on 14 March 1945 from wounds received during the bombing of his house in Dozza, donated it to the Imola General Library who gave it to the Observatory on loan, sine die....."
F. Bònoli (1991) p. 162.
F. Bònoli (1992) p. 135.
A. da Schio (1880).
A. da Schio (1886) p.1347, (1966) p.157
M. Destombes (1966) p.160.
D.A. King (1991a) p. 154.
D.A. King (1991b) p. 3.
L.A. Mayer (1956).
P.J. Renaud (1937).
P. Trento (1989).