used in the Constantinople observatory of Taqi ad-Din. These included ancient instruments such as the armillary sphere, paralactic ruler and astrolabe; medieval Muslim instruments such as the universal astrolabe, azimuthal and mural quadrants, and sextants; and several instruments he invented himself, including the mushabbaha bi'l manattiq, a framed sextant with cords for the determination of the equinoxes similar to what Tycho Brahe later used, and a wooden quadrant for measuring azimuths and elevations. His most important astronomical instrument, however, is the "observational clock", which in his In the Nabk Tree of the Extremity of Thoughts, he describes as "a mechanical clock with three dials which show the hours, the minutes, and the seconds. We divided each minute into five seconds." This was used for measuring the right ascension of the stars. This is considered one of the most important innovations in 16th century practical astronomy, as at the start of the century clocks were not accurate enough to be used for astronomical purposes. A "remarkably modern-looking" terrestrial globe of the Earth, one of the earliest of its kind, was constructed by Taqi ad-Din at the Constantinople observatory of Taqi ad-Din. Observations Taqi ad-Din made use of his new "observational clock" to produce a zij (named Culmination of Thoughts in the Kingdom of Rotating Spheres) more accurate than his predecessors, Tycho Brahe and Nicolaus Copernicus. Taqi ad-Din was also the first astronomer to employ a decimal point notation in his observations rather than the sexagesimal fractions used by his contemporaries and predecessors. He also made use of Al-Biruni's method of "three points observation". In The Culmination of Thoughts in the Kingdom of Rotating Spheres, Taqi ad-Din described the three points as "two of them being in opposition in the ecliptic and the third in any desired place on the ecliptic. He used this method to calculate the eccentricity of the Sun's orbit and the annual motion of the apogee, and so did Tycho Brahe and Copernicus shortly afterwards, though Taqi ad-Din's values were more accurate, due to his observational clock and other more accurate instruments. See also Astronomy in medieval Islam Great Comet of 1577 Taqi ad-Din Muhammad ibn Ma'ruf References Further reading Ahmad Y Hassan, Taqi al-Din and Arabic Mechanical Engineering, Institute for the History of Arabic Science, Aleppo University, 1976, pp. 34–35. Antoine Gautier, L'âge d'or de l'astronomie ottomane, in L'Astronomie, (Monthly magazine created by Camille Flammarion in 1882),