This link details how the ancient Vikings were themselves keen astronomers. As the article details, the Vikings utilized the ever-popular Polaris as a guiding light during sea travel. They would measure the angle relative to Polaris to determine cardinal directions for navigational purposes. During the day, the Vikings would utilize two special types of sundials, one of which could only be used at noon, in order to determine their orientation at sea. Amazingly, they even had what was known as a „sun stone“ to help find the position of the sun during overcast periods.