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    Re: Lunars Tables
    From: Fred Hebard
    Date: 2007 Dec 2, 20:12 -0500

    I don't know where Bruce is.  He was never in the best of health
    while posting here.
    
    Bruce's math has been posted on the list piecemeal.  It's possible
    that Frank Reed summarized it in one posting.
    
    Bruce's method is a direct solution of the clearing problem, rather
    than a solution involving approximations, such as that published by
    Bowditch.  I believe the approximation methods may be quicker than
    Bruce's method, at least for hand calculations, but perhaps not by
    much.  Both go pretty instantaneously on modern computers.
    
    Bruce came up with an ingenious and novel method for accomplishing a
    subtraction between two trignonometric quantities without having to
    transform from logs to antilogs, and then back.  That must make his
    method the shortest of the direct-solution methods using tables and
    pencil and paper.  The advantage of Bruce's method is that it is
    available in one book, today, whereas tables for the approximation
    methods are out of print.
    
    I don't know that anybody uses lunars for actual navigation, with
    accurate Greenwich time so readily available.  Those who have used
    them to calibrate sextants have usually used Frank Reed's online
    lunar clearing calculator, or perhaps computer programs of their own
    that solve the clearing equations directly.  Here, the focus is on
    calibrating the sextant, not practicing clearing by hand.
    
    If you were planning to go to sea and rely upon lunars as a backup or
    primary means of finding longitude, you would want to practice with
    Bruce's tables extensively, until their use became second nature.
    Likewise, for standard sight-reduction tables.
    
    Fred
    
    
    On Nov 30, 2007, at 6:45 PM, Scott Owen wrote:
    
    >
    > Bought a copy of Bruce Starks, Tables for Clearing the Lunar
    > Distance a
    > few weeks ago.  From the archives it looks as though Bruce was a
    > regular
    > contributor but I did not see anything of late.  I have two questions:
    >
    > 1)  Are these the tables most members use for reducing Lunar
    > observations or is there some other preferred method/tables?  [I know
    > there are many methods to do this, I'm just trying to get a feel for
    > what method list members are using and what may be considered the most
    > accurate method.]
    >
    > 2)  Is anyone familiar with the trig/math that Bruce used to derive
    > his
    > lunar tables?  If so, does anyone know if Bruce is amenable to posting
    > it on the list or has it been posted in the past and I just missed
    > it in
    > the archives?
    >
    > Thanks in advance.
    >
    > --Scott
    >
    > >
    
    
    
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