17 February
1723: On 17 February 1723, Johann Tobias Mayer was born.
Mayer was a German astronomer who developed lunar tables that greatly assisted navigators in determining longitude at sea. Mayer also discovered the 'libration' (or apparent wobbling) of the Moon.
Mayer began calculating lunar and solar tables in 1753 and in 1755 he sent them to the British government. These tables were good enough to determine longitude at sea with an accuracy of half a degree.
Mayer's method of determining longitude by lunar distances and a formula for correcting errors in longitude due to atmospheric refraction were published in 1770. He died on 20 February 1762.
