NavList:

A while ago we had an ongoing discussion of what scales were actually used on the Bygrave and the German version, the HR1. Wolfgang just posted an excerpt of a book in German which supplies additional information on this issue. I am attaching pages 166 and 167 of this book. Even without speaking German I think it is clearly stated on page 167 that the inner scale is a log cotangent scale and the other scale is a log cosine scale. Also page 166 states the formulas that are actually solved with these slide rules which identify the scales as a cotangent scale and a cosine scale.
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Some of you may be interested in the linked pages
of "Lehrbuch der Navigation"
Bremen 1943, volume II
They show different aircraft sextants and describe
their use and properties. (in German...)

Most intersting is the last paragraph on mechanical
calculation devices for the celestial triangle,
including HR1.
It reads:
"The altitude slide rule manufactured by Dennert & Pape
has proven useful and was introduced to navy and air
force."
Another hint that MHR1 is not likely to mean "marine" HR

Wolfgang

Pdf documents, zip compressed are linked ~ 5MB
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gl
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