Great Astrolabe

Astrolabes could in theory have been used for navigation, but many, including this one, were too large and heavy for that to be practical. Instead, they were used to map the position of the stars and planets, for calculations, and to study and teach the theory and motion of the heavens.

James Gregory plotted his telescope observations with this astrolabe. He had a special plate made for it, for latitude 56 25, which was close to the accepted latitude of St Andrews in the period.

Credit: Courtesy of the University of St Andrews Libraries and Museums