Early Astronomy in the University of Michigan Collections

Observational armillaries were fairly large astronomical instruments designed to establish the position of celestial bodies in ecliptic coordinates, that is, in their celestial longitude and latitude. In his Astronomiae instauratae mechanica, Tycho Brahe describes various kinds of observational armillaries, including zodiacal armillaries, which could provide the ecliptic coordinates without any calculations, being an improvement on the armillaries described by Hipparchus and Ptolemy because it had only four rings instead of five or six.

Brahe’s Astronomical Instruments

Equatorial Armillaries

Brahe and Kepler