One of them was that set up in the 13th century by the astronomer Nasirüddin Tûsî in Meraga in Iran, which operated for 12 years; another was the one founded at Samarkand by Ulug Bey, the grandson of Timur, in the 15th century where the renowned astronomer Ali Kusçu carried out his studies. A third observatory, and the one that forms the focus of this article, was built in Istanbul during the reign of Sultan Murad III. It was the 16th century. The astronomer Takiyeddin bin Muhammed bin El-Maruf, who is thought to have been of Turkish origin, had completed his studies in Egypt and was appointed chief astronomer by Murad III. Takiyeddin had always dreamed of founding an observatory. So he wrote a letter to Saadeddin Efendi, an historian who wielded great influence with the sultan, emphasizing the need for an observatory for making actual observations rather than merely doing calculations on paper. Grasping the importance of the subject, Saadeddin Efendi obtained permission from the sultan for the founding of an observatory, which went into operation at Tophane in 1575.