'Figure du Pasage de Venus sur le Disque du Soleil', June 1769.
© Science Museum / Science & Society Picture Library
Map print of the world showing the areas on the Earth where the 1769 Transit of Venus 5 Jun could be observed. Engraved by P. Choffard in Paris, the map was produced in 1760 through the effort of the French Astronomer, M. De La Lande. It was produced to publicise this rare event as it offered astronomers a means to accurately measure the size of the Solar System. By timing the event from widely separated latitude on the Earth, it was posible to use geometry to find the distance the Sun. Once measured the distance to the other planets could be calculated from their orbital period around the Sun.