For thousands of years seafarers, who crossed the seas far from land, had only the sky to help them. They learned early on how to use the position of celestial bodies, the sun, moon and stars to guide their course.
The astrolobe is an ancient instrument for estimating the position of the sun and other planets with respect to the horizon and the meridian.
It was perfected by the Arabs and used widely, especially by Portuguese and Spanish seamen, up until the 17th century. Other similar instruments in use from the 16th century were the cross-staff and Davis’ quadrant.