Flamsteed (1646-1719), the first Astronomer Royal, seen through a pyramidal mirror (prism). Viewed from the correct angle, the prism allows the viewer to see the whole picture. Charles II appointed Flamsteed Astronomer Royal in 1675, setting him the task of constructing accurate lunar and stellar tables, which were needed to allow longitude to be calculated at sea, a major navigational difficulty at the time. The Royal Greenwich Observatory was established for the work, which would take Flamsteed the rest of his life to complete. He was determined not to publish anything until he had completed the whole task, which led to disputes with his contemporaries. When finished, Flamsteed's comprehensive star catalogue contained the positions of almost 3000 stars.
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