OK, have a look at the Bris 'sextant'. http://en.wikipedia.org/wiki/Bris_sextant http://en.wikipedia.org/wiki/Bris_sextant Elegant device that enables you to

OK, have a look at the Bris 'sextant'. http://en.wikipedia.org/wiki/Bris_sextant http://en.wikipedia.org/wiki/Bris_sextant Elegant device that enables you to get an accurate Sun altitude at specific times of day, and hence a position fix. No moving parts. I think the 'hack' here is to think through the navigation requirements of someone sailing across an ocean. Do they need to be able to find a position at an arbitrary time (the proper sextant) or would the ability to find a position at some time during daylight be enough? The result is a device that is robust and that can be kept in a 35mm film cassette.