What instrument aided explorers by allowing ship navigators to check their location by charting the position of stars and planets?

The sextant was the instrument that aided explorers by allowing ship navigators to determine their location by measuring the angles between celestial bodies, such as stars and planets, and the horizon. This device enabled navigators to calculate their latitude and longitude, which was essential for accurate navigation on the open sea. By using the sextant in conjunction with precise timekeeping, explorers could chart their positions more effectively and embark on longer voyages with greater confidence.