NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Noell Wilson
Date: 2022 Dec 19, 06:34 -0800
Hi Emmanuel,
I’ll not claim to be an authority but it looks like the “French” T1, T2, and T3 scales roughly correspond to the T<45, T>45, and ST (in that order) scales on my Dietzgen 1734 decimal trig log log slide rule. The same scales are on most 10” engineering slide rules.
My “big” slide rule - a Pickett N4 - has the same Tangent scales as my Dietzgen.
The vertical dotted lines on the French rule look like they’d correspond to the 1’s on the Dietzgen “D” scale. Part of that seems to show in Table II under the T1, T2, T3 table I.
The French scales extend past the limits on the Dietzgen and I can’t follow the booklet enough to see if the French scales are all extended or if they wrap.
So, the French Tangent scales are slightly extended on each end but I don’t think they offer an extra magnitude of values past 5 and 84 degrees.
Regards, Noell
