From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, p. 540

Courtesy of

usayn, Hasan and Muammad

David A. King

asan usayn

FlourishedIsfahan, (Iran), second half of the 17th century

Muammad usayn

FlourishedIsfahan, (Iran), second half of the 17th century

asan usayn and Muammad usayn were two instrument makers in Isfahan, Iran, and were somehow associated with the various better‐known makers of fine astrolabes and other instruments that grace many a museum the world over. Their two names, however, are new to the literature. They made European‐style inclined sundials fitted with compass dials; two instruments made by each one of them are of particular historical interest because the horizontal bases for the sundials are engraved with world maps. These are fitted with complex mathematical grids that preserve direction and distance to Mecca at the center. The former (discovered in 2001) is more carefully engraved than the latter (discovered in 1995), and a third example, unsigned and now missing sundial and compass (known since 1989), may also be by asan usayn. The underlying mathematics and the geographical data used for some 150 localities on each map are entirely within the Islamic tradition; the former is attested in Arabic treatises from 10th and 11th centuries, and the latter is taken from a 15th‐century source. Indeed, Muslim interest in projections preserving direction and distance to the center goes back to abash al‐āsib and Bīrūnī, each of whom wrote on the astrolabe with a melon‐shaped ecliptic on the rete. However, we are still looking for a 17th‐century or earlier Arabic or Persian treatise on the construction of the map‐grids, or indeed for any new information on the school of instrument makers from which these remarkable objects stem.

Selected References

King, David A. (1999). World‐Maps for Finding the Direction and Distance to Mecca: Innovation and Tradition in Islamic Science. Leiden: E. J. Brill.

——— (2004). In Synchrony with the Heavens: Studies in Astronomical Timekeeping and Instrumentation in Medieval Islamic Civilization. Vol. 1, The Call of the Muezzin (Studies I–IX). Leiden: Brill. VIIc (“Safavid Mecca‐Centred World‐Maps–A Third Example and New Light on the Origin of the Grids”).