Eighth to the Sixteenth Century - Rashid Islamic Center

60 • The Making of Islamic Scienceall this, astrology remained popular with rulers and the elite, andthis sometimes produced tensions that spilled over into the relatedarea of astronomy. This may have been the cause of the closing ofthe Istanbul observatory, but there were also other political motivesbehind that incident.Astronomical research required the use of certain instruments.Muslims had inherited some knowledge of instrument making fromPtolemy’s Almagest, but they invented many new instruments over thecourse of eight centuries, including observational instruments as wellas analog computers. Quadrants, altitude sextants, semicircular, rulerinstruments, and other observational tools were used to determinealtitudes and azimuths; armillary instruments were used formeasuring right ascensions and declinations and for longitudes andlatitudes with respect to the ecliptic. Sextants and bipartite arcs, as athird type of observational instrument, were used to determine theangular distances between celestial bodies. Various accounts of theseinstruments provide insights into their improvements. Al-Biruni’spreviously cited work, The Determination of the Coordinates, also providesinformation about developments in various instruments. The useof the mural quadrant, for instance, was an important developmentin practical astronomy, and its accuracy was not surpassed until theuse of optical instruments. The invention of the mural quadrant isgenerally attributed to Tycho Brahe and is named after him; recentscholarship has shown that the so-called Tycho’s Mural Quadrant (orTichonicus) was already in use in the Muslim world during the time ofNasir al-Din al-Tusi; Taqi al-Din’s observatory in Istanbul had a muralquadrant of a 6 m radius, whereas the radius of Tycho’s quadrant wasonly 194 cm (Dizer 2001, 248).Other instruments developed or improved upon by Muslimsinclude the armillary sphere, first described by Ptolemy butapparently never constructed until its use by Muslims. A variation onthis instrument constructed at the Maragha observatory had five ringsand an alidade instead of six rings. This increased the convenience ofuse without reducing accuracy.The most important analog computer used by Muslims wasthe astrolabe. Its origins are definitely pre-Islamic, but it receivedsustained and focused attention by Muslims, who perfected its useand made many improvements in its design. “The ability of Islamic