Flamsteed House in Greenwich Park, London, designed by Christopher Wren on the orders of Charles II as an Observatory. At this date the problem of finding longitude at sea was unsolved and the observatory was built in the expectation that it would be possible to produce tables to enable mariners to plot their position. The first nation to solve the problem would have naval and mercantile advantage. John Flamsteed was the first Astronomer Royal. 17th century copperplate engraving.