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    Re: Graphical lunars
    From: Ken Muldrew
    Date: 2015 Feb 28, 16:21 -0700
    Francis, in 1790 George Margetts published Margetts' Longitude Tables which was a series of graphs that plotted the data in the Cambridge tables for lunar distances. Using this relatively small book one can easily clear a lunar in a few minutes that is accurate to a few seconds. I don't know why this method never took off but as early as 1790 the problem of clearing lunars had been rendered fast and simple to perform.

    On 2015-02-28, at 2:41 PM, Francis Upchurch wrote:

    Thanks Henry,

    This is really a very interesting historical  thing. Just found Dutton 1805 on Google who quotes the original Kelly method as described dating from 1797! So you could do lunar clearance in 1797 easily using these simple graphical techniques? Dutton claims they were accurate to 5’? Perhaps they were not? Otherwise why were they not taken up as routine?

    I shall look into it.

    Thanks again.

    Francis


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