How did Vikings navigate?

The Vikings had explored more of the world than anyone else of their era. Viking explorers were Norse warriors, traders and pirates who raided, explored, traded and settled in wide areas of Europe including Great Britain and Ireland. The Vikings came from Norway, Sweden and Denmark and were great sailors. Unlike most people of the time they were able to navigate by the stars and so cross great oceans. They traveled as far as North America, Africa and the Near East, and colonized Iceland and Greenland. All Vikings were required to own weapons as well as permitted to carry them all the time.