Along with large instruments for observatories, the astronomers developed many devices, almost always conceived for the measurement of time. The celestial globe, the armillary sphere, the plane astrolabe and the astronomical clock offered mobile representations of the sky. In astrolabes and globes, the representation was so accurate that astronomical calculations could be made without recurring to mathematical formulas. Among the instruments for measuring time, the astrolabe was foremost until the 16th century when, with the development of high-quality clocks, its fortune declined. Finally, the armillary sphere was the basic instrument used in teaching astronomy.