NavList:

First off, thanks to everyone who has responded so far. It is amazing how small the spread of estimates is!

Frank said:

"Fascinating concept. You're teasing us by not hinting more at how it works! :) "

Well Frank, with all the smart fellas on this list, I was sure it would take everybody less time figuring it out than it would take me to write out the explanation of how it works. It is very simple really. (It would have to be for me to come up with the idea!)

But if anyone wants to put up their guess on how it works..... well, don't let me stop you ;-) I will post a photograph of it and a schematic when someone gets it right, or close to it.

"And would you like to have this experiment announced outside the NavList community? Or do you prefer to limit it for now?"

I have had eight responses so far. Ideally, I would like twenty or more so I can get some decent statistics. 

Here's a reminder of the link for the movie.

http://www.geoffrey-kolbe.com/docs/sundial_final.mp4