Astronomical instruments are devices used to observe, measure and model the movements of the heavens. They include astrolabes, armillary spheres, celestial globes, orreries, telescopes, quadrants, sextants, transit instruments and sundials, as well as astronomical clocks that show the positions of the sun, moon and stars.
The astrolabe, developed in the ancient Greek world and refined in the medieval Islamic world, was used for calculating time and the positions of stars. Armillary spheres modelled the celestial circles with interlocking rings, while orreries, popularised in eighteenth-century England, demonstrated the motions of the planets around the sun and were favoured as instruments of polite education. The development of the telescope in the early seventeenth century transformed astronomy, and London instrument makers such as John Dollond and his successors, Jesse Ramsden and Troughton & Simms gained international reputations for their work. Collectors value instruments by named makers, early dates, complete fittings and original cases, and condition of lacquer and engraving is significant. Many decorative armillary spheres and globes produced in the twentieth century are reproductions, so careful examination is advisable. Antique astronomical instruments make striking display pieces in libraries and studies.
