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I'm interested in learning about the navigational techniques used by
land geographers in the late 18th and early 19th centuries;
particularly those used by the fur traders exploring the Canadian
West at that time (such as David Thompson, Peter Fidler, Philip
Turnor, etc.).

It appears that there is an active group of enthusiasts here who are
trying their hand at finding longitudes by lunar distances. Through
the excellent articles in the archives, as well as a remarkable paper
by Jeff Gottfred in the Northwest Journal
(http://www.northwestjournal.ca/dtnav.html) where a longitude
calculation is fully worked, I have come to have an understanding of
the technique. Though as Sophocles warned, "One must learn by
doing the thing; for though you think you know it, you have no
certainty until you try".

I would really like to gain an appreciation of the mechanical aspects
of the calculation, as it was done ca. 1800. I know that they used
Merrifield's approximate method for clearing the lunar distance,
using calculated altitudes of the moon and star (with a double
altitude of the sun to establish latitude). But I don't know what their
method of manual calculation was (although I have used log tables to
perform mechanical calculations...long ago). I would like to know
what tables were used by these navigators. Does anyone here know
what tables were included in Maskelyne's Tables Requisite as it
would have appeared in the late 1700's and what precision the
numbers were given to?

   \----------------------------+---------------------------------+   o_,
 O_/ \    Ken Muldrew, PhD      | Voice: (403) 220-5976           |   <\__/7
 <\__  \  Dept. of Cell Biology | Fax:   (403) 270-0617           |     | /
  "\ L  | University of Calgary | kmuldrew@acs.ucalgary.ca        |   / /
   <    +-----------------------+---------------------------------+ / /
               Morning coffee recapitulate phylogeny               L/

   

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