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    Re: Dip uncertainty
    From: Alexandre Eremenko
    Date: 2004 Dec 6, 18:23 -0500

    On Mon, 6 Dec 2004, Bruce Stark wrote:
    > Climb on the buoy and look at the horizon through the
    > prism. The angle between the horizon and where you see
    > it through the prism will
    > be huge.
    > Now go twenty miles away, and from a height where you can
    > see both the prism
    > and the true horizon, look (you'll need a powerful telescope)
    > at the prism.
    > The horizon you see through the
    > prism will be only slightly out of line with
    > the true horizon.
    IF you are able to see the horizon from 20 miles THROUGH the
    prism, the correction to
    the normal dip in these two experiments
    will be the SAME, namely, the angle by which the ray is turned
    by the prism.
    Its another matter that from 20 miles, no matter how powerful
    your scope is (and assuming ideally transparent atmosphere,
    better no atmosphere at all) you will not be able to see the horizon
    THROUGH your prism. What you will see is some spot of the sea surface
    near the prism.
    Just draw a picture, assuming that the angle of deflection
    of the ray by the prism is the same in both experiments.

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