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    Re: Refraction near the Horizon ? Observation vs. Calculation
    From: Paul Hirose
    Date: 2013 Apr 08, 12:55 -0700

    Marcel Tschudin wrote:
    > The refraction formula is indeed the one from Bennett in a form which
    > provides the resutls in degrees. Bennett provided also a second
    > formula for further improving the result of this first formula. Does
    > your N.A. 1998 edition makes reference to it?
    There's no reference to a more accurate formula.
    The formula (including the corrections for pressure and temperature)
    duplicates the almanac's high and low altitude refraction
    tables within 0.1′ for the values I tried, assuming 10 C and 1010 mb. I
    didn't test the almanac table A4 corrections for nonstandard conditions.
    > Just in case these finding should one day be documented in a paper:
    > How is the correct reference to this N.A. edition?
    1998 Nautical Almanac Commercial Edition, published jointly by Paradise
    Cay Publication and Celestaire Inc., "Sight Reduction Procedures"
    chapter, p. 280.
    Does anyone have a newer almanac? Are the refraction and dip formulae
    still included?
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