Constantinople observatory of Taqi ad-Din

The Istanbul observatory of al-Din was one of the largest astronomical observatories to be built in the Islamic world. However, it only existed for several years before it was destroyed.

History

In 1574, Murad III became the Sultan of the Ottoman Empire. The empire's chief astronomer, Taqi al-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 Istanbul 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 al-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, al-Din had hoped to update the old astronomical tables describing the motion of the planets, sun, and moon.

Tragically, 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" al-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. Al-Din was able to carry on his observations for a few more years but eventually opponents of the observatory and prognostication from the heavens prevailed and the observatory was destroyed in 1580. Other sources give the "rise of a clerical faction," which opposed or at least was indifferent to science, and specifically to "the recommendation of the Chief Mufti" of the Ottomans, as the explanation for the destruction of the observatory.

Instruments

Taqi al-Din invented a framed sextant similar to what Tycho Brahe later used as shown in the picture.

Taqi al-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 Istanbul observatory of al-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 Nabik Tree of the Extremity of Thoughts, he describes as "a mechanical clock with three dials which show the hours, the minutes, and the seconds." This was the first clock to measure time in seconds, and he used it for astronomical purposes, specifically for measuring the right ascension of the stars. This is considered one of the most important innovations in 16th century practical astronomy, as previous clocks were not accurate enough to be used for astronomical purposes. This was also the first astronomical clock to be powered by springs. He further improved the observational clock, as described in his Sidrat al-muntaha, using only one dial to represent the hours, minutes and seconds, describing it as "a mechanical clock with a dial showing the hours, minutes and seconds and we divided every minute into five seconds."

A "remarkably modern-looking" terrestrial globe of the Earth, one of the earliest of its kind, was constructed by Taqi al-Din at the Istanbul observatory of al-Din. Although Taqi al-Din had also invented a rudimentary telescope some time before 1574, it is unknown whether or not he employed the instrument for his later astronomical observations at the Istanbul observatory of al-Din from 1577.

Observations

Taqi al-Din invented a mechanical "observational clock" with three dials for the hours, minutes and seconds.

Taqi al-Din made use of his new "observational clock" to produce a zij (named Unbored Pearl) and astronomical catalogues more accurate than those of his contemporaries, Tycho Brahe and Nicolaus Copernicus. Taqi al-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 Abū Rayhān al-Bīrūnī's method of "three points observation". In The Nabk Tree, Taqi al-Din described the three points as "two of them being in opposition in the ecliptic and the third in any desired place." 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 al-Din's values were more accurate, due to his his observational clock and other more accurate instruments.

Further reading

• David A. King, Taki al-Din in EI (2nd ed.), vol. 10, pp. 132-3
• Ahmad Y Hassan, Taqi al-Din and Arabic Mechanical Engineering, Instiute 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), december 2005, volume 119.