Stars in Casiopeia, November 1883.
© Science Museum / Science & Society Picture Library
Photograph taken in November 1883 by the Henry brothers, Paul & Prosper, using the astrographic telescope at the Paris Observatory. Showing a star field in the constellation of Casiopeia, the image is an early example of photography being used to survey and map the heavens. Pioneered by the Henry brothers in France, the technique was developed into an international project to map the night sky in unprecedented detail. Known as the Carte du Ciel, the mammoth undertaking was not completed until the middle years of the twentieth century. Today it forms a valuable resource for comparison with present-day high precision surveys of the position of stars using spacecraft.