Instruments

How the sky was measured and modelled — from the astrolabe to the armillary sphere, the instruments that turned looking up into knowing.

In this reading room

• The Astrolabe — An ancient instrument for measuring the altitude of stars and planets and for solving problems of time and position in the sky. Often called the first analogue computer, it let a single hand-held disc tell the time, find a body’s place and model the turning heavens.
• The Armillary Sphere — A model of the heavens built from a nest of rings, each standing for an important circle of the sky — the celestial equator, the ecliptic, the tropics and the horizon. It shows, in three dimensions, how the sky is organised around a central Earth or Sun.