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    Re: 60° Pendulum Astrolabe
    From: UNK
    Date: 2016 Jul 20, 19:48 -0700

    It depends on what "accuracy" means. I'll give the designers and builders of the astrolabe full credit and say that if you set up perfectly, reduce the sight perfectly, knock down, set up at the same spot, sight, and reduce a second time you may well get within 15 feet.

    But, if you take the same care and take the two sights 1000 miles apart, you could be off 100 meters because of variations of the earth's mass at different locations. Look at the thread "NOW what?" In August 2015 for details.

    Bottom line of my point is that a perfect pendulum depends on the same forces as a perfect liquid AH and a perfect level. They can all cause an error from a perfect triangulated ground survey because "down" is not necessarily the same as what we assume, and casually refer to as, "straight down".

    Going out of my area, I know that coriolis forces act on weather near the earth surface. Do they affect a stationary pendulum and would that change the "accuracy" from the poles to the equator?
    Regards, Noell

       
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