NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: CelNav without sextants
From: Alexandre Eremenko
Date: 2004 Nov 2, 16:04 -0500
From: Alexandre Eremenko
Date: 2004 Nov 2, 16:04 -0500
Dave, I disagree with what you said. Namely, with the "logic". Suppose indeed that the methods I mentioned gave the SAME precision as the methods based on the use of sextant. The sextant-based methods will still have an advantage of their wider applicability. (The rise and set events occur only few times a day... occultations are rare etc. At the time needed for observation, the objects can be obscured by clouds etc.) Second, I was not talking of the same precision, but the same "order of magnitude". In other words. It is hard to imagine a ship doing an ocean crossing without a compass. So I DO assume there is a compass (and maps). So dead reckoning is available. Columbus experience shows that you can do very well with dead reckoning only. The question was whether you can improve on this. So "100 miles error" is something non-acceptable. But "10 miles error" is something very useful on an ocean crossing. I conjecture that one can do reasonably well (say 10 miles) with WATCH and ALMANACH ONLY. (Assuming there are days in your trip with reasonably good weather:-) In fact, my question stated as precisely as I can and as technically as I can is this: "To what precision can you hope to get a position line from timing (GMT) of a sunset/sunrise"? Alex.