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    Re: Celestial Navigation without a sextant.
    From: Peter Fogg
    Date: 2008 Mar 9, 14:38 +1100

    George wrote:
    >  So timing sunrise/sunset will
    >  never provide a precise value for longitude. But if a rough ball-park figure
    >  will suffice, it could do the job.
    Here's a thought: if the time of apparent sunrise/sunset was observed regularly;
    the extent of the difference or inaccuracy shown by observation
    compared to calculated data could be evaluated on a regular basis and
    contrasted with other information about position.
    Given that the effects of anomalous refraction can constitute a
    significant constraint upon the accuracy of observations taken from
    the deck of a small boat, thus from within the lowest band of
    atmosphere, and that there is no way of knowing whether they are
    present, let alone the extent of inaccuracy introduced;
    If this known difference between observed and calculated
    sunrise/sunset should change, could it be a indication of the extent
    of anomalous refraction likely to affect sights taken close to that
    time, eg; star sights just before dawn, or just after sunset?
    Particularly sights taken in that direction?
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