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    Re: 60° Pendulum Astrolabe
    From: Mark Coady
    Date: 2016 Jul 21, 10:20 -0700

    GPS accuracy..mmmm..I would guess not....

    Let me ask this in the form of another question....a little knowledge is a dangerous thing. I would love to understand it better. If we are claiming GPS like accuracy from this type of celestial observation,(neglecting device error) aren't we faced with a few fundametal issues?:
    1. Geodesy problems? Distortion in our astronomical observations caused by indeterminate gravitational field distortion? E.G. mass concentration and a tilted plumb? I think bermuda is an oft cited reference where a surface measured 15 miles vs and astronomically observed 15 miles might be off by .25 miles?
    2. Our inability to calculate fully all atmospheric effects, such as changes in refraction.
    3. The limitations of accuracy of the necessarily imperfect references used to calculate.

    BTW...with gravitational fields in mind... I understand starlight is bent by the suns gravitational field. Are star observations affected by the gravitational field of the sun? Does any bending of light change based on sun position relative to the rotating star field? Is this compensated for in Almanac data or is it so small that it is negligable.

    MC

       
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