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    Re: Longitude by Sunrise
    From: John Karl
    Date: 2010 Feb 3, 17:50 -0800

    Jeremy,
    Your sunrise longitude results don't seem out of bounds to me. Both these sextantless "longitude-by-sunrise" (or sunset) and my "zero-altitude" shot can easily suffer from the same possible anomalous refraction conditions. The difference is the zero-altitude sight is a true LOP, independent of assumed latitude. BTW, did you correct for temp & pressure? They can easily account for your results.

    Moreover, the Almanac's dip tables don't account for anomalous refraction effects which can throw the horizon off by 3' or more.

    So yes, these are somewhat emergency sights, but also possibly entertaining at sunset happy hour -- well, for certain types of sailors.

    You and Berson are lucky to live near Greenport, it looks wonderful compared to Wisconsin. Outside my window I see pickup trucks driving on my sailing grounds.

    My "Sextantless CN" article should come out in this summer's Ocean Voyager.
    JK
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