NavList:

I wrote previously:
"What of navigation then? Enter the "mariner's astrolabe". That's how they're known to historians, at least, but it's an insult to the magnificent terrestrial astrolabes! These were tools, and very simple tools at that. Stick a standard scale of angles, like a common protractor on a disk. Mount an arm on a point of rotation at the center of the disk. Affix sighting peeps on that arm. Hang the disk from some sort of loose mounting point so that it may swing free enough to seek a gravitational vertical but not so freely that it oscillates with the motion of the ship. And that's about it! You now have a mariner's astrolabe."

I've been thinking about this, and maybe there's some unspoken history in here. I mentioned a "loose mounting point". This actually goes a long way toward explaining why mariner's astrolables and the instruments that followed were handheld. A human observer can develop a natural talent at damping out oscillations. We do this without planning or thinking. This is the original problem of "cybernetics" --the loose hand at the helm that manages a ship's rudder without over-compensating, or worse, driving it into forced periodic oscillations, was once a fairly difficult thing to automate. Similarly when you hold a hanging astrolabe, you have to give it some freedom to move but also let your grip on its hanging chain stay loose in a certain fashion so that it doesn't end up swinging madly with every little roll and pitch of the vessel. For how many centuries was the "light touch" of a human hand the best solution to the problem of cancelling out those semi-chaotic oscillations driven by ocean waves and other natural, turbulent forces?

Frank Reed