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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2024 Mar 7, 20:02 -0800
Alexandre wrote
Then a question arises, how they handled the trigonometric formula for solution of a spherical triangle.
For example, in the formula
sin(h) = sin(latitude)·sin(declination) + cos(latitude)·cos(declination)·cos(t),
In the 19th century trigonometric formulas were NOT used. if, for example, you were doing a long by chron you would find the hour angle by following the appropriate TEXT rule in the book. In this case it is Rule XCVl. Step by step instructions were given. I am guessing that many 19th century mariners learnt navigation by rote. Perhaps what we should be looking for is when did the authors of text books start using trigonometrical formulas?
In an old text book of mine is the quotation "Although he wrote it all by rote he did not write it right."
David C
