Bygrave slide rule

It solved the so-called celestial triangle accurately to about one minute of arc and quickly enough for aerial navigation.

The slide rule was constructed as two coaxial tubes with spiral scales, like the Fuller's cylindrical slide rules, with yet another tube on the outside carrying the cursors.

[1] During the Second World War, a closely related version was produced in Germany by Dennert & Pape as the HR1, MHR1 and HR2.

He later completed a round the world cruise in his yacht Gipsy Moth IV.

Sir Francis Chichester wrote about these exploits in his autobiography, entitled The Lonely Sea and the Sky.