The century and a half which separated Nasir al-Din's observatory in Maragha (1262) from the one constructed by Ulugh Beg in Samarqand (1420) was not without interest. In 1300 the Ilkhanid ruler Ghazan Khan (1295–1304) founded a complex of institutions outside his capital of Tabriz. At the centre of this development was a mausoleum, around which he erected a mosque, a Sufi lodge (khanqah), two madrasas, a hospital, a library, a law school, a primary school, a bathhouse, and an observatory. Like Hulagu, Ghazan Khan was interested in both the science and the pseudoscience, and, after visiting Maragha, he designed an observatory which contained a hemispherical instrument for solar observations, a library, and a school for teaching the rational sciences. Ghazan Khan's Tabriz Observatory, however, was much smaller than the one at Maragha. With a limited programme and a shorter lifespan, its principal achievement was the creation of a new calendar and a new era. The epoch of the Khani Era was 1302, and its calendar was quite similar to the Jalali of ‘Umar Khayyam. The year began on the vernal equinox (21 March) but the names of the Khani months were Turkish rather than Persian. The new era and calendar, however, were not widely adopted, remaining in use only through the reign of the last Ilkhanid ruler, Abu Sa‘id Bahadur (1316–36).

In 1325 Rukn al-Din Ahmad, a pious sayyid, founded in the Iranian city of Yazd a charitable complex consisting of a madrasa, a mosque, a hospital, a library, and what a local historian called the Rasad-i Waqt wa Sa‘at (The Observatory of the Time and Hour). Although ‘observatory’ suggests a building or buildings, observational instruments, and astronomers, where the movements of the heavenly bodies were tracked, recorded, and interpreted, the actual description (and the name – ‘time and hour’) indicates more a muwaqqit khana (timekeeper's office) than an astronomical institution. From the description in Tarikh-i Kabir (a local history), the structure seems to have been a giant astronomical water clock.