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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.



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