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    Re: Celestial Navigation In The Gps Age: Typos?
    From: Bill B
    Date: 2017 Aug 31, 15:36 -0400

    On 8/31/2017 1:23 PM, Tony Oz wrote:
    > Also I wonder why the /Chapter 10, Accuracy/ advises to use the
    > different corrections for the lower and upper limbs of the Sun (the
    > -13.5' and +18.5' respectively). Yes, their sum is the very familiar 32'
    > of the Sun's diameter, but why they are different?
    The simple answer to your question of why they are different in two parts.
    1. When we calculate the Hc of a body (especially the sun and moon) we
    are calculating the distance from the horizon to the CENTER of the body.
    We need to add to the a lower limb observation and subtract from an
    upper limb observation to determine the center
    2. The lower limb is closer to the horizon, therefore it experiences a
    greater shift due to refraction than the upper limb.
    That being said, Karl uses words such as "relaxing accuracy
    requirements,"quick and dirty," and "cavalier" to describe his
    "shortcuts." In other words, "YMCA or slop pool," and "close only counts
    in horse shoes and hang grenades."
    Hope that answers your question.

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