NavList:

David Pike, and everyone else who contributed on this in the past few days, thank you for your efforts and explanations! I haven't had time to read all of it, let alone digest it, but I'm looking forward to doing that today. It's amazing how completely this instrument breaks the old "duck" rule. Duck rule (sextant variant): if it looks like a sextant and quacks (is adjusted) like a sextant, then it must be a sextant. Yet this stadimeter is distinctly different from a standard sextant despite the persuasive superficial similarities!

Incidentally, I'm glad I admitted I didn't understand how this thing worked. Sometimes you just have to stand up and say "I don't get it..." :)

Frank Reed