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New Light on the Zīij al‐Safāa'ih of Abū Jacfar al‐Khāzin
... They consist only of plates of various sizes for visualizing the epicycles and deferents, so that they appear to have intended basically to reflect the Ptolemaic tradition in the Planetary Hypotheses; to cite only a few: Abū Ja'far al-Khāzin in the Safā'iḥ zīj (fl. the first half of the tenth century) (on the basis of the unique manuscript preserved in Srinagar, Kashmir, Research Library, no. 314: the plates are drawn on folios 88v-95r, with a precedent brief description of the arrangement of the plates on f. 88r; see, also, King 1980;Calvo 2004;King 2004-2005, Ibn al-Samḥ (d. 1035 c.e.), Ibn al-Zarqālluh (d. ...
The paper brings into light and discusses a concentric solar model briefly described in Chapter 5 of Section III of ‘Abd al-Raḥmān al-Khāzinī’s On experimental astronomy, a treatise embedded in the prolegomenon of his comprehensive Mu‘tabar zīj, completed about 1121 c.e. In it, the Sun is assumed to rotate on the circumference of a circle concentric with the Earth and coplanar with the ecliptic, but the motion of the vector joining the Earth and Sun is monitored by a small eccentric hypocycle. The ratio between the distance of the hypocycle’s center from the Earth and the hypocycle’s radius is equal to the solar eccentricity in the eccentric model. The model is to account for the constancy of the apparent diameter of the solar disk as held by Ptolemy. The source of the model is unknown. Since the mechanism employed in it clearly resembles the pin-and-slot device, whose use in mechanical astronomical instruments has a long history from the Antikythera Mechanism to the medieval solar, lunar, and planetary equatoria and dials, we argue that the solar model can be positioned within this long-standing tradition and considered the result of the correct understanding of some Byzantine prototype and thus a typical example of the transmission of astronomical ideas via media of the material culture.
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