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    Re: Watch into Compass?
    From: Frank Reed CT
    Date: 2004 Feb 12, 22:45 EST
    "I think the accuracy is much better, probably within five degrees and most of that is from casually pointing the tiny watch hand at the bright spot in the sky."

    Sometimes yes, but other times, no way. You should also try it "double-blind" sometime. Find yourself a kid "who doesn't know any better" and teach the trick. Then go out somewhere, spin said kid around until dizzy, and then try to have the kid find the compass directions. No coaching! How far off are you and your navigational guinea pig?

    Until you have procured your guinea pig, consider this: in most of June and early July, the Sun's declination is within a degree of 23. For that dec, the Sun's azimuth in your latitude (you said 43 N) reaches 270, due west, at about 4:10 (-ish) local apparent time. If you try the watch trick at this point, it will tell you that South is close to azimuth 209. That's pretty far off already. This ignores equation of time and zone correction which could easily add another 10 degree error on top of that. So that's possibly 39 degrees error in direction for an observer well away from the tropics. It's worse farther south. Yes, it's very roughly in the right direction, but I think you would agree that it's not much better than you would get by guessing. A person who knows the Sun rises generally in the east and sets generally in the west wouldn't be much farther off under these circumstances than someone using the watch trick. It's not a very good compass!

    The watch trick works reasonably well whenever the Sun is close to the meridian, and it also works reasonably well whenever the Sun stays a long way from the zenith. Otherwise it can be waaay off.

    Frank E. Reed
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois

       
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