Viking Astronomy
Russell M. Heglund
Leif Karlsen, author of Secrets of the Viking Navigators, was the guest speaker at the March 10 member meeting. Vikings regularly crossed to Iceland, Greenland and North America in the 10th and 11th centuries,out of sight of land without magnetic com-pass. Leif discussed the navigation methods that Vikings may have used to cross the open sea. Most crossings were made in summer, when the rising and setting of the sun could be used to determine the ship.s course. At night, stars gave direction--Polaris was well known, and north could be determined on clear nights.
The Vikings were latitude sailors. Since Iceland and Greenland were straight west of Norway, by keeping on the same latitude throughout the voyage, they could reach their destination. They would go to a particular port in Norway known to be the same latitude as their destination. Before departing, they would note which stars crossed the zenith each night and which stars passed close to the horizon. These stars would be the reference stars for latitude during the voyage. They would also note the rise and set locations of the sun, relative to their planned course, for daytime navigation. If the sun were obscured by sea mist, they may have used a device called a .sunstone. to find it.
Leif brought some devices he constructed and demon-strated how the Vikings may have used the sun to navigate: a horizon board (to locate points of the compass), shadow pins (to get direction), and a sunstone (to locate the sun in a mist).
Horizon Board (Courtesy Leif Karlsen)
The horizon board was a board divided into eight sections (directions) and then oriented towards the rising and setting locations of the sun.
If the sun was obscured by mist (often a sea mist hung over the horizon), a sunstone could be used to locate it. The sunstone was a piece of calcite crystal (Icelandic spar), which Leif had mounted to a board. He had placed a black dot on the top of the crystal. When you look from the bottom, it appears there are two dots. When the sun was obscured, you rotate the crystal until the “two” dots appear to have equal density. At that point the crystal will be pointing to the sun. (Calcite is a birefringent material, which will split incident rays into two beams— thereby we see two images.)
Sunstone (Courtesy Leif Karlsen)
Shadow Pins (Courtesy Lief Karlsen)
Also discussed was a shadow pin method: The sun’s shadow was plotted on a board. Equal shadow lengths on either side of noon were plotted and connected for east/west direction. Bisecting the line gave north direction.
Members were able to examine the navigation devices and beautiful sunstones Leif had brought. The talk reminded us that much of our knowledge of astronomy grew out of a desire to locate ourselves in the trackless sea, as well as to locate our place in the universe (still on-going). Note: All diagrams are from Secrets of the Viking Navigators by Leif K. Karlsen, One Earth Press 2003, used by permission.