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    Re: Thoughts on Celestial.
    From: John Huth
    Date: 2012 Nov 1, 18:45 -0400
    The cocked hat issue also arises in triangulation with magnetic compasses (on land or in coastal piloting) with students.  The "good enough" issue often is my answer.   I think it's actually helpful to get experience with many situations.   When I backpack, I do triangulation not so much because I'm lost, but I feel like it gives me a 'tune-up'.     In one particular case, it was a life-saver.   I was backpacking over a very dry region and trying to find a spring some distance off the trail.   It was in a canyon-land region with a confusing maze of creek valleys dissecting the region.   I had to triangulate my position as it was nearly impossible to get a good fix from visual references, so I relied on mountains and hills where I could get a reliable shot.   I found that I was traveling faster than we actually estimated from dead reckoning (going downhill). I came to a spot where I suspected the spring was located nearby.   My brother-in-law was certain we hadn't reached it.   I tried to persuade him to stay put while I investigated a promising lead, but he didn't believe me.   Ultimately it turned out to be the spring, but he was already hiking away, with no water and the next spring a good 10 miles away (it was 95 degreed F out).   

    My son managed to catch up with him.   He already had some disorientation from a mild heat exhaustion.   There's no telling what might have happened had we not found that spring. 

    In this case, my triangulation was 'good enough' to convince me that our dead reckoning assumptions were incorrect.



    On Thu, Nov 1, 2012 at 5:21 PM, Alan S <alan202@verizon.net> wrote:

    Re the ongoing discussion of Celestial Navigation, might a "landlocked navigator", one who as Mr.Gilbert might have noted "stuck close to his desk, and never went to sea" add his own thoughts? It is, by the way, quite interesting to read the thoughts of people who know what they are talking about, Chief Franklin, Lu Abel, Greg Rudzinski, Brad Morris et al.

    Speaking for myself, I tend to stand on the beach, when I can get to one, shooting such "celestial bodies" as might pass within view, most often AM and PM sun, sometimes sun and moon, and rarely planets and stars. I get my DR position from a hand held GPS, which I guess is usually within 10' of where I actually am. I have a decent sextant, and Astra 111B, so I assume any screw-ups, there are some beauts, derive from operator error. When I use the sextant properly, and do not misread the NA or transpose numbers, my calculated fixes are often inside 5 NM of GPS coordinates, unfortunately not always, there is that ever present "operator error".

    In any case, respecting open ocean or high seas celestial navigation, based on what I've read, I would think that fixes obtained from sextant shots that were within 5 NM of actual position, consistently within, would be more than adequate as a practical matter. Concerning navigation within sight of land (piloting) the story would be or could be markedly different, but out to sea, it's a very large ocean, with a lot of distance between continents and islands, there being few ships floating around thereon. As to whether one's fix is inside or outside the cocked hat, re navigating on the high seas, I suppose that beating the proverbial dead horse is one of several ways of passing the time.

    Alan


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