Astronomiæ instauratæ mechanica

Tycho Brahes astronomical instruments

The aim of this project is to exhibit the astronomical inventions of Tycho Brahe, especially the instruments through which the stars and planets could be observed and by which distances and ascensions could be measured.
There are three types of instruments: 1. quadrants and sextants used for determining altitudes and azimuths; 2. armillary instruments for measuring right ascensions and declinations, or longitudes and latitudes with respect to the ecliptic; and 3. instruments designed for the determination of angular distances between celestial bodies (sextants and the bipartite arc).
The instruments of Tycho Brahe represent a major achievement in astronomical science, because they provided much more accurate readings than previously possible, and on the basis of Tycho Brahe's observations Kepler determined the laws of planetary motions and from these laws Newton discovered the law of gravity. Not until the invention of the telescope some years after Tycho Brahe's death was it possible to get more accurate readings.
The instruments were built by Tycho Brahe and his staff between the 1570's and his death in 1601, many of them during his stay on the island of Hven (between 1576 and 1597).  All of Tycho Brahe's instruments are lost. After his death they were kept in a cellar, where they were destroyed during the uprisings in Prague in 1619. The great globe ended up at the Round Tower in Copenhagen, where it was destroyed in the fire of 1728.  Of the buildings at Hven only few remains are left, but a replica of the garden of Uraniborg and the foundations for the instruments at Stjerneborg can be seen. In 1992 a new Tycho Brahe exhibition was inaugurated on Hven.

Tycho Brahe himself described his instruments in the book Astronomiæ instauratæ mecanica, Wandsbek 1598. The illustrations and the Latin text here are digital reproductions from this work (now at the Royal Library of Copenhagen).

The Danish translations are taken from Nordisk Astronomisk Tidsskrift, 1933-1954 (see the bibliography). The Royal Library wishes to express its thanks to the editorial board for permission to use these translations. Instrument 26, 27 and 29, however, are translated by Helle Damgaard Andersen.

The English translation is taken from H. Ræder, E. Strömgren & B. Strömgren, Tycho Brahe's Description of his Instruments and Scientific Work, København 1946 (Det Kongelige Danske Videnskabernes Selskab). The Royal Libary wishes to express its thanks to the Royal Academy of Science for permission to use this translation. The Royal Libary also wishes to thank Peter Kristian Moesgaard for permission to quote his brief description of the specific background for the original publication of the book.
This site has been created by Helle Damgaard Andersen and the photographs were taken by Karsten Bundgaard, .The Royal Library, photographic studio


There are some difficulties with the measurements given by Tycho Brahe. The following units are used: a foot; a span; a passus geometricus; and a cubit. One (Tychonian) foot seems to have been 25,9 cm; a span a ¾ foot; a passus geometricus 6 feet and a cubit 1 ½ foot.