Captain James Cook
Cook the navigator
This map shows the outline of New Zealand as charted by Cook in 1770. Superimposed on it, in red, is the actual outline of the two islands taken from a 20th-century Admiralty chart.
Cook completed the survey in only six months. Although the shape of the two islands is extremely accurate, they are actually about 32 km (20 miles) too far to the east. This is because it was still difficult to determine longitude precisely.
Where am I?
Latitude – the imaginary lines that run horizontally around the world – was easy enough to determine, but longitude, the lines running vertically, was not.
On Cook's first voyage he took a book of lunar tables produced by the Royal Observatory in Greenwich. This helped him to find his longitude by measuring astronomical angles.
'My trusty friend the watch'
Cook took one made by Larcum Kendall known as K1. He called it 'my trusty friend the watch'. Cook's success with K1 was instrumental in making the time method of finding longitude popular and following his voyages it was adopted on many naval expeditions.
Although chronometers were a faster and more accurate way of determining longitude, they were expensive, so lunar tables continued to be produced by the Royal Observatory for mariners until the early 20th century.
Centre for instrument making
This carved figure of a midshipman holding an octant stood outside William Heather's shop at 157 Leadenhall Street in the City of London. An octant was used for measuring the height of heavenly bodies above the horizon, in order to find latitude accurately.
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