Out at sea, there are no landmarks. In the Middle Ages, sailors had special instruments that used the position of the Sun and stars to tell them where they were. These included compasses, astrolabes and cross-staffs.
Amazing! The first astrolabes were made 1,500 years ago! Indian and Arab astronomers used pocket-sized instruments called astrolabes in the AD 500s.
Is it true? Astrolabes only worked at night.
No. You could use the position of the Sun instead of the stars, when you were sailing during the day. You looked at its position compared to the horizon.
What is the pole star?
The only star which doesn’t appear to move is above the North Pole. Sailors could tell where they were by looking at the pole star – it’s lowest in the sky at the Equator.
How did an astrolabe work?
An astrolabe had two discs, one with a star map, and the other with measuring lines and a pointer. You compared them with the Sun or a star and the horizon to work out your position.
Picture Credit : Google