Indo-Persian bras astrolabe, 1666.
© Science Museum / Science & Society Picture Library
This bras Islamic astrolabe was made by Jamal al-Din at Lahore, Pakistan. An astrolabe is in esence a model of the universe that an astronomer could hold in their hands. From its origins in the Ancient World, Islamic astronomers developed the astrolabe and its use spread. Popular in Medieval and Renaisance Europe, its many uses included timekeeping, astrology and surveying. The two-dimensional depiction of the heavens used on this instrument is achieved using the mathematical technique of stereographic projection. This back view shows the moveable sighting arm, called the 'alidade', which is used to measure the position of the stars or for surveying.