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    Re: 2-Body Fix -- take three
    From: Peter Hakel
    Date: 2009 Nov 8, 13:57 -0800


    From: George Huxtable <george{at}hux.me.uk>
    To: navlist@fer3.com
    Sent: Sun, November 8, 2009 11:38:50 AM
    Subject: [NavList 10503] Re: 2-Body Fix -- take three

    [parts deleted by PH]

    Now for a separate issue, if John will forgive me for adding another twist.
    I can't resist bringing out an old hobby-horse of mine once again,
    concerning 7.5f. John wrote-
    "We're using the convention that LHAs are measured westward to 360, and that
    west Lons are negative."

    Some reader-confusion is added because we are having to add or subtract
    amounts, longitude and hour-angle, which are of the same quantity (angle
    measured with respect to the Earth's polar axis) but which are defined as
    going positive in opposite directions. I wonder if anyone can think of
    another example, in any field of mensuration, where this occurs? I can't.

    ------------------------------------------------------------------------------------------------------------

    Eq. 7.5e reads:
    Lon = LHA1 - GHA1
    this comes from:
    Lon = - ( GHA1 - LHA1 )
    in which the expression in () is self-evident and the extra minus sign addresses the sign convention.  This should address any possible confusion.

    Combining Arabic script and numerals has a left-to-right vs. right-to-left issue.


    Peter Hakel



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