Constantinople Observatory of Taqi ad-Din  The Constantinople observatory of Taqi ad-Din, founded in Constantinople (today Istanbul) by Taqi ad-Din Muhammad ibn Ma'ruf in 1577, was one of the largest astronomical observatories in medieval world. However, it only existed for a few years and was destroyed in 1580. In 1574, Murad III became the Sultan of the Ottoman Empire. The empire's chief astronomer, Taqi ad-Din, petitioned the Sultan to finance the building of a great observatory to rival Ulugh Beg's Samarkand observatory. The Sultan approved, and construction was completed in 1577, at nearly the same time as Tycho Brahe's observatory at Uraniborg. This observatory consisted of two large structures perched on a hill overlooking the European section of Constantinople and offering a wide view of the night sky. Much like a modern institution, the main building was reserved for the library and the living quarters of the staff, while the smaller building housed a collection of instruments built by Taqi ad-Din. These included a giant armillary sphere and an accurate mechanical astronomical clock for measuring the position and speed of the planets. With these instruments, Taqi ad-Din had hoped to update the old astronomical tables describing the motion of the planets, sun, and moon. The observatory did not survive to advance the development of astronomy in the Muslim world. Within months of the observatory's completion, a comet with an enormous tail appeared in the sky and Sultan Murad III demanded a prognostication about it from his astronomer. "Working day and night without food and rest" Taqi ad-Din studied the comet and came up with the prediction that it was "an indication of well-being and splendor," and would mean a "conquest of Persia". Unfortunately, instead of well-being a devastating plague followed in some parts of the empire, and several important persons died. Astronomy was a respected and approved science among the Islamic clergy of the Ottoman Empire, yet the same could not be said with regard to astrology, a field which is considered to be divination and thus against sharia. In order to prevent its further use for astrological purposes, they successfully sought the observatory's destruction. This happened just as the king of Denmark built an observatory for Tycho Brahe that would pave the way for Kepler's elucidation of the orbits of planets. Taqi ad-Din wrote an important treatise on astronomical instruments entitled the "Observational Instruments of the Emperor's Catalogue", which describes the astronomical instruments used in the Constantinople observatory of Taqi ad-Din.