February 1995 page 15
J. W. Findlay

Proof of the Accuracy of the Capuchin and Regiomontanus Dials using the Polar Triangle of Navigation

A mathematical demonstration using spherical trigonometry to prove the timekeeping accuracy of the Capuchin and Regiomontanus portable sundials, complete with diagrams and derivations.
Dials: Portable, Mathematics of Dialling