Sailors measured the height of the stars in the sky to track their progress. Sailors also used their knowledge of the constellations to navigate. Because constellations change seasonally, mariners had to know which constellations were visible in the sky at different times of the year in each hemisphere.

What invention helped sailors to navigate?

One of these was the astrolabe, a portable device used by sailors to help them find their way. By measuring the distance of the sun and stars above the horizon, the astrolabe helped determine latitude, an important tool in navigation.

What constellation helps sailors to navigate the sea?

The star Polaris, often called either the "Pole Star" or the "North Star", is treated specially due to its proximity to the north celestial pole.