Timurid
Ulugh Beg's Observatory
The great sextant of Timurid Samarqand
834 AH / c. 1430 CE
Educational historical reconstructionWhere
The observatory of Ulugh Beg, Samarqand, Transoxiana
39.6753, 67.0055 · View on OpenStreetMap
Background
At Samarqand in Transoxiana, the splendid Timurid capital, the prince Ulugh Beg (rahimahu Allah), grandson of the conqueror Timur and himself a gifted astronomer and mathematician, built around 1420-1430 one of the greatest observatories of the medieval world and made his city the high point of Islamic astronomy. He had already raised a madrasa at the Registan, and to it and to the observatory he gathered the finest astronomers and mathematicians of the age: Ghiyath al-Din Jamshid al-Kashi, the great computational astronomer; Qadi Zada al-Rumi, his teacher and the observatory's senior scholar; and the young Ali Qushji, who would carry the work forward after the others had gone (rahimahum Allah). The observatory was a great round building of several storeys, and its central instrument was a colossal meridian arc, a sextant some forty metres in radius sunk into the bedrock along a north-south trench and finely graduated, with which the altitudes of the sun, moon, planets and stars could be measured as they crossed the meridian with an accuracy unmatched in its day. Alongside it the astronomers worked with armillary spheres, quadrants and astrolabes. From this labour came the Zij-i Sultani (also called the Zij-i Gurgani), a catalogue of more than a thousand stars observed afresh rather than copied from Ptolemy, together with astronomical and trigonometric tables of a precision not surpassed for centuries and used and admired far beyond the Muslim world, reaching the astronomers of Europe. Ulugh Beg was a rare example of a ruler who was himself a working scientist; but his absorption in scholarship cost him politically, and in 849 AH / 1449 CE he was killed in a revolt led by his own son. After his death the observatory was abandoned and fell into ruin, its very site forgotten until the great sextant's rock-cut foundations were excavated in 1908. This scene depicts the observatory at work by night: the curved track of the colossal meridian arc within its trench, astronomers bent over astrolabes, armillaries and tables, and beyond the parapet the turquoise domes and portals of Samarqand under a sky thick with stars. In keeping with the project's ethics any figures are anonymous and at a distance.
What you see
Sunk into a deep brick-lined trench in the middle of the terrace runs a colossal curved rail, a meridian arc graduated in fine degrees and flanked by twin staircases. This is the great Fakhri sextant, the largest instrument of the observatory, on which the sun and stars were tracked as they crossed the meridian line.
A seated scholar turns a brass astrolabe in his hands while open tables lie on the low table before him; another stands beside a tall armillary sphere of nested rings. These are naked-eye instruments, astrolabes, quadrants and armillaries, and there is no telescope, which would not be invented for nearly two centuries.
Beyond the parapet rise the ribbed turquoise domes, tall portals and minarets of a great city catching the last light of dusk. This is Samarqand, the Timurid capital of Transoxiana, then among the most splendid cities of the world and a centre of learning.
This is the observatory of Ulugh Beg (rahimahu Allah), the prince and scholar-ruler of Samarqand and grandson of the conqueror Timur, who was himself a working astronomer and mathematician and gathered the finest scholars of the age around this great arc.
Charts and tables of figures are spread across the wooden tables, lit by oil lanterns against the deepening night. This is an institution built for patient, precise measurement of the heavens, not for worship or war, and its observations ran night after night.
From the work done at this arc came the Zij-i Sultani, a catalogue of more than a thousand stars and a set of astronomical tables more accurate than any before them. Ghiyath al-Din al-Kashi, Qadi Zada al-Rumi and Ali Qushji (rahimahum Allah) laboured here under the prince's patronage.
Overhead the Milky Way arches across a sky thick with stars, the very object of all this labour. The observatory marks the high point of Islamic astronomy, an empire that prized knowledge and a court that made Samarqand a beacon of it.
Further reading & cross-references
The Zij-i Sultani (the Zij of Ulugh Beg), preface and tables, c. 1437 CE: The observatory's own product: used for the star-catalogue of more than a thousand stars, the trigonometric tables and the company of astronomers named in its preface.
Accounts of Ulugh Beg and his astronomers (al-Kashi's letters, the biographers): Used for the prince-astronomer, the assembling of al-Kashi, Qadi Zada al-Rumi and Ali Qushji, and the workings of the institution; al-Kashi's letters describe the court's learning directly.
Histories of Timurid Samarqand and the chronicles of Ulugh Beg's reign and death: Used for the city as the Timurid capital and centre of learning, and for Ulugh Beg's killing in 849 AH / 1449 CE and the observatory's later abandonment.
Studies of Islamic astronomy and the Fakhri sextant of the observatory: Used for the colossal meridian arc, its radius and graduation, the armillaries and quadrants, and the accuracy of the work; non-confessional, cited for technical detail only.
The excavated foundations of the great sextant (Vyatkin, 1908; extant, material): The rock-cut remains of the meridian arc constrain the depiction of the instrument and the trench; cited for material confirmation only.
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