Avicenna’s Achievments in Astronomy in Medieval Islamic periods
Subject Areas : The Journal of Islamic History and Civilisation
سید محمد مظفّری
1
(
ندارد
)
Keywords: observational astronomy, total declination, ups and downs
, 
, of star, average of itinerary,
Abstract :
This paper gives a critical review of Avicenna’s Astronomy intheoretical and observational aspects. Theoretically, it investigates hismodel for the prime and second motions of the heavens, which havebeen propounded in his Dānishnāma cAlā’ī as well as in al-Najāt. Inthis model, he geometrically and with the strict insistence on theAristotelian dogma in the configuration of the planets’ orbs, i.e. theapplication of the only uniform circular motion, explains that how thePrime Mover is pertinent to the Firmament and the minor orbs of theplanets. In the second aspect, the only observational quantitymeasured by him, that is, his magnitude, 23º;33,30, for totaldeclination, is mentioned, which with accompany of the othermagnitudes gained by his Greek and Muslim predecessors had madehim to believe in changing total declination. Another aspect of hiswork, that is, the synthesis of two aforementioned aspects appears inhis Solar Model, described in the astronomical part of al-Shifā', wherehe attempted to construct a theoretical model for the solar motion bythe combination of five orbs so that it is able to justify theobservational evidence of the change in total declination.
