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Mathematical Treasure: Tycho Brahe's Work and Observatory

Frank J. Swetz (The Pennsylvania State University)

In 1666, Albert Curtz (1600-1671), a Jesuit priest, astronomer, and great admirer of Tycho Brahe’s work, published Historia caelestis, a collection of Brahe’s observations and writings.

Title page of Historia caelestis by Albert Curtz, 1666

The frontispiece contains illustrations of Uraniborg, Brahe’s castle and observatory. He named it after Urania, the muse of astronomy.

Frontispiece of Historia caelestis by Albert Curtz, 1666

In 1576, King Fredrick II of Denmark had given Tycho Brahe (1546-1601) the Island of Hven in the Danish Sound. He became the feudal master of the island and its people. In four years, Brahe constructed his home and observatory, Uraniborg, and equipped it with his instruments. It also served as a laboratory for alchemy. In essence, it became the first modern research center in Europe. From this ideal location for viewing the night sky, Brahe and his assistants began to collect the most accurate astronomical data then available. A colored print from the work Civitates orbis terrarum by Georg Braun and Franz Hogenberg (1598) shows Brahe’s empire:

Colored print of Hven from Civitates orbis terrarum by Georg Braun and Franz Hogenberg, 1598

Below is shown a detailed copper print of Uraniborg which illustrates the grandeur of the estate. This illustration was created by the Dutch cartographer Joan Blaeu in 1662.

Copper print of Uraniborg by Joan Blaeu, 1662

Perhaps the most noteworthy scientific instrument at Uraniborg was the “Great Quadrant”. The quadrant was made of brass, had a radius of 194 cm, and was fixed to a north-south facing wall. The following illustration from Astronomiae instauratae mechanica (1602) depicts the quadrant being used. The observer sights across the meridian at a heavenly body viewed through an aperture in the facing wall. He notes the meridian measurement as his assistant, standing below, marks the time.

Image of Great Quadrant from Astronomiae instauratae mechanica, 1602

Tycho Brahe’s instruments were the most accurate for taking celestial measurements in this period of history. Illustrations of his major instruments were given in his Astronomiae instauratae mechanica (1602). In addition to his "Great Quadrant" (shown above), two more are shown here:

The images above are presented courtesy of the History of Science Collections, University of Oklahoma Libraries.

Index to Mathematical Treasures

Frank J. Swetz (The Pennsylvania State University), "Mathematical Treasure: Tycho Brahe's Work and Observatory," Convergence (October 2018)