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    Re: Ted Gerrard's book
    From: Michael Daly
    Date: 2007 Nov 19, 01:38 -0500

    coralline algae wrote:
    > I see in other messages on this list that occultations were used
    > as a sort of almanac, a way to mark a point in time,  when
    > clocks were still not accurate enough to for surveying or
    > navigation.  Here is where I will shamelessy speculate that
    > almanacs of that time may have stated something like there
    > will be an occultation of a specific ecliptic star by the moon at
    > approx midnight?
    Think of a lunar occultation as a special case of a lunar distance -
    where the distance is precisely 0.00 degrees.  Otherwise, the method is
    essentially the same and requires the same level of precision in an
    almanac table that specifies the location of the moon relative to the
    stars.  Appulses are similar but there is more room for error - the star
    will not "turn off" and provide a well-defined point in time.
    Halley's method can only be as accurate as his lunar position knowledge.
      No one published tables at that time (as Maskelyne did after 1767).
    There was the raw data that was coming out of Flamsteed's observations
    and other observers that may have been accumulating data.  Newton and
    Halley published Flamsteed's data without his permission in 1712 but
    what Halley used in the 1699 timeframe I don't know offhand.
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