t opside V olume 120 , I s s u e 2
P a ge 21
An Auxiliarist Explores Sunstone Navigation
by Tim Marks photos and graphic by COMO Joseph Giannattasio
Theory is one thing , practice is another . To find out , Commodore Joe Giannattasio , an experienced Auxiliary coxswain and pilot , decided to put the sunstone to the test . “ When you are looking through a sunstone you are not only looking for light , but also for images .” Joe explains it this way , “ If you make a single mark on the top of the crystal and look through it from below , then two marks will appear . You then hold the crystal up to the sky and rotate the crystal until the two marks have exactly the same intensity or darkness . At that angle , the obtuse surface indicates the direction of the sun .” Using a chunk of calcite from Iceland spar and a thin strip of electrical tape , he created a simple device that projected a doublelined image onto the opposite side of the crystal . By rotating the crystal until the two lines had the same intensity , he was able to determine the direction of the sun , even when it was below the horizon . The results were impressive : he was able to locate the sun within two degrees , even in dark or cloudy conditions . Giannattasio , who is also a member of The Explorers Club in NYC , proposes that Viking sailors could have used the crystal to keep track of the sun ’ s position in dark twilight or cloudy conditions , and then turn the ship in the relative direction they wanted to go .
COMO Joe Giannattasio displaying an Icelandic spar Sunstone .
But could the Vikings have used this technology on their ships , which were prone to rolling and pitching in the rough seas ? It would have been a demanding task , requiring skill and concentration , but it is not beyond the realm of possibility . After all , the Vikings were masterful seafarers who knew how to use the natural world to their advantage . They turned simple materials into powerful tools , and in doing so , they conquered the seas .
Auxiliarist Explores Sunstone Navigation
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