File:Benedetti(1575)-(dial).svg

Summary

Benedetti, an impoverished nobleman worked as a mathematician at the court of Savola. His book which describes this method , De gnomonum umbrarumque solarium usu published in 1574. It decscribes a method for displaying the legal hours, that is equal hours as we use today, while most people still used unequal hours which divided the hours of daylight into 12 equal hours- but they would change as the year progressed. Benedettis method divides the quadrant into 15° segments. Two construction are made: a parallel horizontal line that defines the tan h distances, and a gnomonic polar line GT which represents sin φ.

• 1: Draw a quadrant GRB, with 15° segnments. GR is horizontal.
• 2: A parallel horizontal line is drawn from PE, and ticks made where it bissects the 15° rays.
• 3: GX is the latitude. T is the crossing point with PE. GTE is the gnomonic triangle.
• 4: The length GT is copied to the bottom of E giving the point F.
• 4b: The hour lines are drawn from F- and the dial is complete.

Benedetti included instructions for drawing a point gnomon so unequal hours could be plotted.

Licensing

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