 Image courtesy of One Earth Press . Alignment of the Calcite. From Karlsen's book: A spot placed on the top face of the calcite rhomb appears as two images from below. One image is that of the ordinary ray (it stays in one position) and the other image is that of the extraordinary ray (it changes position) as the rhomb is rotated. When the rhomb is aligned to the sun the two dots will appear side by side and be of equal tone. As one moves off of alignment, one spot will fade. Note that the seperation of the two images is greater as the thickness of the calcite increases. A pointer stick placed along the long side of the rhomb aids in aligning with a point on the horizon (or one on each end as shown).  Image courtesy of One Earth Press . A dot placed on the top surface of the rhomb appears as two dots when viewed from below. See a little YouTube movie on Viking Navigation by NASASciFiles; about 3 minutes into the video there is a demonstration of the Viking Sunstone (in this case, calcite rhomb) just as Karlsen describes it: Viking Sunstone. For an overview of Karlsen's method see his article on Viking Navigation (pdf file, 1.76 MB). For much more detail, read more in Leif K. Karlsen's book "Secrets of the Viking Navigators." | |