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On 19 Oct 2010 at 16:23, George Huxtable wrote:

> We've discussed this matter on the list before, but I can't put my finger
> on the postings. As I remember, Frank expressed the view that reiteration
> would seldom if ever be necessary. If I have it right, that view seems to
> be in some doubt..

One of the topics that has come up on this subject before is the apparent
agreement among the lunar cognescenti of the late 18th and early 19th
centuries that calculated altitudes was the preferred tecnique for land-
based navigation (with a hand-held sextant). William Wales and Philip
Turnor both taught this method (both of whom were well aquainted with
Maskelyne, though I'm not sure if I have ever seen any direct evidence
that Maskelyne also advocated for this method). Patterson instructed
Merriwether Lewis not to bother with altitudes on the Voyage of Discovery.

I don't know if this was because of the non-tropical nature of these land-
based voyages or because land-travel is inherently more amenable to
calculated altitudes (better longitude by account, better latitude
knowledge (you can always use a star if you miss the sun), or just because
you have to take 3 sights anyway (time, latitude, & lunar distance) so you
may as well get time and latitude in the bargain). Even when land-based
navigators used the sun for their time sight, immediately before taking a
lunar, they would still calculate the altitude of the sun when working
their lunar.

Ken Muldrew.

   

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