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Culture and history · The sky-measurers

Taqi al-Din and the Istanbul Observatory: observing with a clock

The observatory that began observing at Tophane in 1577 was demolished three years later. Explore Taqi al-Din's instruments, the role of the mechanical clock in observation, decimal trigonometric tables and the debated reasons for the demolition, and put the sky-measurers' relay in order.

  • 18 min
  • 2 simulations
  • Mini quiz

Updated:

Preview

The question

In Seyyid Lokman's Shahanshahnama (Book of the King of Kings), produced at the end of the 16th century, there is a famous miniature painting. Turbaned astronomers have gathered in a room: one holds an astrolabe, one is writing, one is examining a globe; on the table stands a mechanical clock. The scene shows the observatory that began observing at Tophane, in Istanbul, in 1577. But three years later the building was razed to the ground. Why was it built, what did it measure, and why was it destroyed?

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Ordering

The sky-measurers in order

Order the cards by dragging them or moving them with the keyboard, then press Check.

Prediction

Predict first

Roughly how many years do you think passed between Ptolemy (2nd century AD) and Ulugh Beg's catalogue in Samarkand?

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Protractor

The noon Sun at the equinox

Turn the arm with the slider; the arrow keys move it 1 degree at a time. The horizontal line is the southern horizon. When you're ready, press Check.

Prediction

Predict first

In a city farther north than Istanbul, how does the noon Sun look on the same equinox day?

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Frequently asked

5 questions

Why was the Istanbul Observatory demolished?

The building was pulled down in January 1580 on the sultan's orders; that much is certain. The reasons are debated: historians discuss the interpretation of the 1577 comet, objections from religious scholars, rivalry at court and the cost. Reducing it to a single cause would be too simple.

Did Taqi al-Din build a telescope before Galileo?

There is no reliable evidence that he did. Taqi al-Din wrote a book on optics, but no telescope appears in the sources about the observatory. A telescope was first turned to the sky in 1609.

Why are the instruments of Tycho Brahe and Taqi al-Din so similar?

There is no evidence that they corresponded. Both were solving the same problem, drawing on a shared heritage from Ptolemy and the observatories of the Islamic world. Similarity on its own is not proof of copying or contact.

Why was a clock important for observing the sky?

The sky turns 15° every hour, so 4 minutes correspond to 1 degree. The time between two stars crossing the meridian gives the angle between them. That is why every minute of error in the clock becomes an error of 0.25° in position.

Did astronomy end in the Ottoman Empire when the observatory was demolished?

No. The office of chief astronomer continued, calendars and tables were still produced, and Taqi al-Din's works were copied and read. However, the observatory's early closure prevented long series of observations from being kept up.