Ulugh Beg was a poor politician and warrior. Just a year after becoming leader of the central Asian kingdom of Transoxiana, he was deposed by his son – then beheaded. Yet he was one of the top scientists and educators of his time. He built a school and observatory at the capital city of Samarkand. Astronomers there made highly accurate measurements of the heavens – two centuries before the invention of the telescope.

Construction of the observatory began in 1420, and was completed a few years later. The complex consisted of a tall, round building that housed a variety of instruments.

The main one was a quadrant – a quarter of a circle. It was the largest one ever built – 130 feet from center to rim. Its base was carved into a hillside, making it highly stable. And it was aligned with the meridian – the north-south line that passes directly overhead. Astronomers used precise markings on the instrument to measure the positions of the Moon, Sun, planets, and stars.

From those observations, they determined the length of a year to within a minute of the modern value. They calculated the tilt of Earth’s axis. And they published the first major star catalog in 1600 years.

The observatory was destroyed soon after Ulugh Beg was killed. It was rediscovered in 1908 – a long-forgotten astronomical treasure.

Script by Damond Benningfield