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    Re: Lunars: how to use the prop.log tables?
    From: Ed Popko
    Date: 2016 Aug 30, 15:05 -0700

    Tony,

    I'm unskilled at explaining math sequences but I'll give it a try. If you search the NavList archives you will find some very good discussions about why prop logs came to be and how tables were created. Jeff Gottfred's "Lunar tables - use of prop logs" is a very good post.  See: http://fer3.com/arc/m2.aspx/Lunar-tables-use-prop-logs-Gottfred-jan-1995-w804   for a complete explanation.

    So it boils down to this ..

    pLogt = pLogd - pLogD

    Where ...

    D is total change in LD distance from first time (12:00) to last time (15:00) in bracket. Three hours or 60x60x3=10800 seconds.

    Using your post data ...

    D = 84° 35.2' - 82° 56.8'
       = 1° 38.4'

    Looking 1° 38.4' up in table ...
    pLogD =   2766

    and ...


    d is total change in LD distance from First time (12:00) to your unknown time of lunar sight
    d = 84° 35.2' - 83° 00.0'
      = 1 35.2'
    Looking 1 35.2' up in table ...
    pLogd = 2623

    Thus ...

    The pLogt is their difference
    pLogt = 2766 - 2623
              = 143

    Looking up 143 in table falls between tabulated 142 and 145,  so I guess it is about 02:54:09

    Add this offset (time of your lunar from first time bracket)

                            12:00:00
                         + 02:54:09
                           -----------
    Time of lunar  12:54:09

    Ed Popko

       
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