|That's not even much of a swell, but the freeboard is impressively low, no?|
|Icelandic spar crystal is apparently the thing, but I wonder if a pair of Oakleys might work.|
|The Alderney Stone: Remember geometry? Yeah, that's a factor here.|
See the polarization effect and compare to the date and the direction. It's a sort of early and rough sight reduction: celestial with a glassy rock, and no compass. Not everyone buys that this is what the sunstone was and this is how it was used, but it's an interesting find, nonetheless.
|Knowing the gnomon doesn't go on the front lawn is half the battle.|
Another surprise from the article is that the stone suspected to be a sunstone, or to have been used as such, was found from an English ship sunk in 1592, a good two centuries after the introduction of magnetic compasses on most European seagoing ships. What was unknown, as clearly as the optical principles on which the sunstone itself worked, were the terrestrial effects of magnetic variation and the ship's habit of creating deviation (beyond being aware that iron made the needle twitch).
|Iron balls are essential to the compensating binnacle. No joke.|
A good hand with eyeball navigation and a backstaff or even the latest astrolabe could correct for some of these hazards to navigation, but perhaps the sunstone was insurance. Mariners have always been a conservative lot, unwilling to abandon older, proven technologies even when more modern and allegedly superior ones exist...or virtually exist. Like knowing how to swim even if you religiously wear a PFD, perhaps the compass and sunstone combo will be eventually found to be the navigational belt and suspenders of 16th-century...and beyond...seafaring.
|I have these and know how to use them. Will that be the case in even 25 years?|
I maintain that the prudent mariner proposing to venture across the brine avail themselves of all the tools of navigation they can, if only because even a passing familiarity with some of these older methods ties together the concepts underlying all navigation, and makes for a better interpretation of whatever Mr. G.P. System is insisting upon is one's real location.