This instrument is a replica of the oldest European astrolabe described by Marcel Destombes, dating from 980 (cf. M. C.: Un Astrolabe Carolingien et l'Origine de nos Chiffres Arabes, in: Archives Internationales d'Histoire des Sciences 1962, No. 58/59, pp. 3-45). The diameter of the original instrument is 15.2 cm. It comes from the territory of the Marquisate of Barcelona, which belonged to the Frankish Empire in the 10th century, which explains the engraving "ROMA ET FRANCIA" and the latitude 41° 30' on the inlay plate.
Lupitus Barchinonensis (also Sunifred Llobet or Seniofred Llobet), the archdeacon of the Mark, is assumed to be the designer. He was instrumental in conveying Arabic mathematics to the Christian world. He corresponded with Gerbert of Aurillac (c. 950-1003), later Pope Sylvester II. In a letter from 984, Gerbert asked Lupitus to translate an Arabic astronomical treatise, which has gone down in scientific history under the Latin title Sententiae astrolabii.
The original instrument has star positions that do not quite match the accuracy of the engravings. In the reconstruction, these star pointers were partly corrected (for the 10th century) and partly adjusted to secondary stars to not change the rete's overall impression too much. For example, star point no. 3 certainly means Aldebaran (alfa Tau), but the position is close to the small star lambda Tau, which was then also used for the replica.
The complete description of the instrument as PDF for download
