What instrument used stars and the horizon to determine latitude and longitude?

The sextant is a navigation instrument that plays a crucial role in determining a mariner's latitude and longitude by measuring angles between celestial objects and the horizon. It allows navigators to take precise readings of the position of stars, the sun, or the moon relative to the horizon, which is essential for calculating their geographical location at sea.

When a navigator uses a sextant, they aim the instrument at a celestial body (such as a star) and read the angle of its elevation above the horizon. This angle measurement can then be used, along with the time of the observation, to determine the observer’s latitude. For longitude, sailors would additionally need to know the time of the observation, requiring accurate timekeeping with a chronometer.

While the astrolabe also serves as a tool for measuring celestial angles, it is primarily used for locating the altitude of stars and is not as practical as the sextant for maritime navigation. The octant was an earlier tool for measuring angles but lacked the precision of the sextant. A compass, on the other hand, is used for orientation and direction but does not provide a means to calculate latitude or longitude based on celestial observations.

Thus, the sextant is specifically designed for the precise astronomical measurements needed