Improved Ancient Instruments

Timelines of Events

• 130 BCE

  • Hipparchus published a star catalog with more than 850 star positions.

• 150 CE

  • In the Almagest, Ptolemy publishes a star catalog that expands on Hipparchus's work and is regarded for more than a thousand years as the standard work on astronomy.

• 964 CE

  • Abd al-Rahman al-Sufi adds the first references to galaxies in his star catalog.

• 1577

  • Tycho Brahe's star catalog records a nova, demonstrating that the "fixed stars" do change and are not eternal.

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Improved Instruments

• Ptolemy's Almagest was the world's standard authority on star positions for over 1,000 years.

• Ptolemy's work was influential in the Islamic world until the 15th century, when the Mongol ruler Ulugh Beg demonstrated that many of the Almagest's data were incorrect.

• Ulugh Beg, the grandson of Mongol conqueror Timur, was only 16 years old when he became ruler of the family's ancestral seat in Samarkand (modern-day Uzbekistan) in 1409.

  • He established a new madrasa, an educational facility, and invited scholars from all over the world to study there in an effort to establish the city as a renowned center of learning.

• Ulugh Beg had a personal interest in astronomy, and it may have been this interest that led him to order the construction of the largest observatory in the history of the world after discovering significant errors in the Almagest's star positions.

  • It took five years to build and was finished in 1429. It is situated on a hill to the north of the city.
  • Along with his group of astronomers and mathematicians, he started work on creating a new star catalog there.

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Giant Instruments

• Ptolemy’s catalog had largely been derived from the work of Hipparchus, and many of its star positions were not based on fresh observations.
• Ulugh Beg constructed the observatory on a massive scale.
  • Fakhri sextant is 61⁄2-ft (2-m) wide.
  • Its radius was thought to be greater than 130 feet (40 meters).
  • The instrument was placed in a curved trench along the north-south meridian and kept underground to protect it from earthquakes.
• In 1437, Zij-i Sultani (The Sultan’s Catalog of Stars) was published.
  • Of the 1,022 stars included in the Almagest, Ulugh Beg corrected the positions of 922.
  • Zij-i Sultani also contained new measurements for the solar year, planetary motion, and the axial tilt of Earth.
  • This data became very important, enabling the prediction of eclipses, the time of sunrise and sunset, and the altitude of celestial bodies, which were needed to navigate.
• Ulugh Beg's death in 1449 led to the observatory's destruction, and it wasn't until 1908 that it was discovered.

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