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    Re: Lunars: how to use the prop.log tables?
    From: Tony Oz
    Date: 2016 Sep 1, 09:23 -0700

    Thanks, Robin.

    Here’s a modified segment of the explanation at http://fer3.com/arc/m2.aspx/Lunars-how-use-proplog-tables-EdPopko-aug-2016-g36381

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

    Using your post data ...

    12:00 UT, 84° 35'.2, PL 2620

    pLogD =   2620

    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 = 2766

    Thus ...

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

    The difference between 2623 calculated directly and 2620 from the Almanac propagates through and changes the final result slightly

    I'm sure Ed was right about the value of plog D.

    D is NOT from the Almanac, it should be calculated as a "width" between the tabulated brackets:

    84° 35.2' - 82° 56.8' = 1° 38.4'

    because D is the whole change of the lunar distance (that will happen during the full 3 hours between the brackets) from which we need to find a part corresponding to the actual change that happened since the first tabulated bracket.

    So plog D = plog(1° 38.4') = 2623.

    Further is just my nitpicking: because the resulting plog t = 143 is two-thirds closer to the tabulated value of 142 than to 145 I must interpolate the time t two-thirds closer to 02:54:12 from 02:54:06, and rather than picking the middle of the interval (i.e. 02:54:09) I must take it as 02:54:10.

    The final value of UTC of the lunar must be 14:54:10.

    Please comment.

    Regards,

    Tony

       
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