A fine example of this most interesting of diagrams showing the operation of a sundial, published by Franz Ritter, the progenitor of the famous and rare "sundial map." This plate was designed to be used as a base for a sundial when correctly oriented east-west.
With a correctly-positioned sundial, one could use this sheet of paper to tell time. The chart is particularly interesting for how it incorporates the signs of the zodiac onto the map, showing how their maximum declination above or below the equator is related to the axial tilt of the earth. The boundaries of the map are shown as the tropics of Cancer and Capricorn.
Additional details give the chart further use for differentiating the signs of the zodiac. A list at the bottom names all of the opposing signs. Attractive diagrams show jumping stags on the side.
Franz Ritter is most well-known for his "gnomonic" world map, that is, a map that is projected from the north pole and follows the shadow cast by a sundial. This most unusual of world maps appears alongside this presented plate in his treatise on sundials.
Since these plates were intended for use as sundials, very few have survived until the modern era. The plate is rare.
Ritter was a German mathematician, cartographer, and astronomer, active in in the first part of the 17th century.
Ritter's most noteworthy accomplishment was his development of an unusual gnomic projection and his so-called “sundial” world map.
A native of Nuremberg, He had studied under Johann Praetorius at the University of Altdorf. Ritter specialized in the design and manufacture of astrolabes, sundials, and other astronomical, horological and cartographical instruments.