Tycho's great globe, about 1.6 meter in radius. Over 10 years in the making, this instrument came in service in late 1580. Most of the work involved making the hollow wooden globe as perfectly spherical as possible, after which it was covered in brass plates.
The globe had two primary scientific uses; it came to be used to record the position of stars observed by Tycho. By 1595 he had 1000 accurately observed stars inscribed on the globe. However, it was originally intended as a computational device. By means of auxiliary circles, the local azimuth/altitude coordinates, as measured with Tycho's instruments, were converted into the conventional celestial coordinates used to record stellar and planetary positions.
Thoren, V.E. 1973, Journal for the History of Astronomy, 4, 25.
Wesley, W.G. 1978, Journal for the History of Astronomy, 9, 42.
-Written and last revised 11 November 1998 by paulchar@ucar.edu.