The Samarqand Observatory (begun in 1420) and the Zij al-Sultani (completed in 1440) were the high points in the history of Islamic astronomy. After Samarqand observatories were founded in the two great early-modern Islamic empires – one in the Ottoman Empire in 1577 and five in the Mughal Empire between 1728 and 1734. In neither state, however, did the Ottoman or Mughal astronomers substantially surpass the achievements of Ulugh Beg and his men – not in instrument design, observational accuracy, or mathematical creativity. Nevertheless, the Ottoman and Mughal astronomers played an important role in the development of the heavenly sciences as they grappled with the flawed system they had inherited, working to bridge the gap between the Ptolemaic, geocentric theories of the first millennium and the Copernican, heliocentric concepts of the late second millennium.

The Ottoman Empire (c. 1300–1923) was the first and longest lived of the three early-modern states that ruled west and south Asia from c. 1500 to 1800. Unlike the other two – the Safavid Empire (1501–1722) in Iran or the Mughal Empire (1526–1739) in India – the Ottomans did not rule a defined geographical entity. Rather, by the late sixteenth century their empire included an enormous but heterogeneous collection of lands and people in the eastern Mediterranean, stretching from Iraq and Anatolia in the east through Syria, Egypt, the Arabian peninsula, Hungary, and the Balkans to North Africa in the west. Osman (1281–1326), the founder of the dynasty, was the ruler of a small Seljuq successor state in western Anatolia. He and his followers were Muslim Turks, descendants of the Central Asian Seljuqs who had defeated the Abbasids at Baghdad (1055) and had established a successful and far-flung dynasty. Malik Shah, builder of the Isfahan Observatory, had been one of the most important Seljuq rulers. In the early fourteenth century Osman and his warriors expanded their nascent state east across Anatolia and west into the Balkans. Under Bayezid I (1389–1402), however, their advance was halted. Timur, the great Central Asia conqueror, defeated the Ottomans at Ankara (1402), capturing and later killing Bayezid.

The first half of the fifteenth century, between the death of Bayezid I (1402) and the accession of Mehmed II (1444–6, 1451–88), was a time of disruption and dissension. Timur had ended Ottoman control of Anatolia, and it was not easily re-established.