Bürgi's clocks were a great improvement in accuracy as they were correct to within a minute a day. These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before. A mechanical weight-driven astronomical clock with a verge-and-foliot escapement, a striking train of gears, an alarm, and a representation of the moon's phases was described by the Ottoman engineer Taqi al-Din in his book, The Brightest Stars for the Construction of Mechanical Clocks (Al-Kawākib al-durriyya fī wadh' al-bankāmat al-dawriyya), published in 1556-1559.[23] Similarly to earlier 15th-century European alarm clocks,[24][25] it was capable of sounding at a specified time, achieved by placing a peg on the dial wheel At the requested time, the peg activated a ringing device The clock had three dials which indicated hours, degrees and minutes He later made an observational clock for the Istanbul observatory of Taqi al-Din (1577–1580), describing it as "a mechanical clock with three dials which show the hours, the minutes, and the seconds." This was an important innovation in 16th-century practical astronomy, as at the start of the century clocks were not accurate enough to be used for astronomical purposes.[26] French rococo bracket clocks, (Museum of Time, Besançon) The next development in accuracy occurred after 1656 with the invention of the pendulum clock Galileo had the idea to use a swinging bob to regulate the motion of a time telling device earlier in the 17th century Christiaan Huygens, however, is usually credited as the inventor He determined the mathematical formula that related pendulum length to time (99.38 cm or 39.13 inches for the one second movement) and had the first pendulum-driven clock made In 1670, the English clockmaker William Clement created the anchor escapement, an improvement over Huygens' crown escapement Within just one generation, minute hands and then second hands were added. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day This clock could not contain a pendulum, which would be virtually useless on a rocking ship Many European governments offered a large prize for anyone that could determine longitude accurately; for example, Great Britain offered 20,000 pounds, equivalent to millions of dollars today The reward was eventually claimed in 1761 by John Harrison, who dedicated his life to improving the accuracy of his clocks His H5 clock was in error by less than 5 seconds over 10 weeks.[27] The excitement over the pendulum clock had attracted the attention of designers resulting in a proliferation of clock forms Notably, the longcase clock (also known as the grandfather clock) was created to house the pendulum and works
