Yaʿqūb ibn Ṭāriq

Yaʿqūb ibn Ṭāriq (died c. 796 AD) was an 8th-century Persian astronomer and mathematician who lived in Baghdad.

Works ascribed to Yaʿqūb ibn Ṭāriq include:

• Zīj maḥlūl fī al‐Sindhind li‐daraja daraja ("Astronomical tables in the Sindhind resolved for each degree"),
• Tarkīb al‐aflāk ("Arrangement of the orbs"),
• Kitāb al‐ʿilal ("Rationales"),
• Taqṭīʿkardajāt al‐jayb ("Distribution of the kardajas of the sine"), and
• Mā irtafaʿa min qaws niṣf al‐nahār ("Elevation along the arc of the meridian").

An astrological work called Al‐maqālāt (Chapters) is also ascribed to him by an unreliable source.

The Zīj, written around 770, was based on a Sanskrit work  thought to be similar to the Brāhmasphuṭasiddhānta.  This work was brought to the court of al-Mansūr from Sind, reportedly by an Indian astronomer named Kankah. 

The Tarkīb al‐aflāk dealt with cosmography, that is, the placement and sizes of the heavenly bodies. Its estimates of the sizes and distances of the heavenly bodies were tabulated in al-Bīrūnī's work on India; according to him, Yaʿqūb ibn Ṭāriq gave the radius of the Earth as 1,050 farsakhs, the diameter of the Moon and Mercury as 5,000 farsakhs (4.8 Earth radii), and the diameter of the other heavenly bodies (Venus, the Sun, Mars, Jupiter, and Saturn) as 20,000 farsakhs(19.0 Earth radii.)