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which was before midnight. The comparison was too casual to allow a measurement of longitude differences, but the account shows that the principle was still understood. In the 12th century, astronomical tables were prepared for a number of European cities, based on the work of al-Zarqali in Toledo. These had to be adapted to the meridian of each city, and it is recorded that the lunar eclipse of September 12, 1178 was used to establish the longitude

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