Published as an accompaniment to Kepler’s Rudolphine Tables, this bifurcated design allowed Eckebrecht to add a pair of vertical indices, making it easier to adjust baseline astronomical data to specific locations anywhere on Earth. The tables themselves, which plotted the movements of some fourteen thousand stars relative to the moon and planets, provided the most accurate astronomical measures ever taken, and the first derived from a geometrically accurate model of the solar system. Kepler—having accepted the heliocentric premise of the Copernican system—had seen the truth of it when using his own telescope to confirm the results of Galileo’s direct observations. With his demonstration that planetary orbits were slightly elliptical and were followed at varying speeds, Kepler brought theory into harmony with observable reality, resolving the conflicts between understanding and appearance that first attracted the attention of Copernicus.
To a royal patron competing against rival kings for dominion in the New World, a system such as Kepler’s proved invaluable. With a large and spectacularly reliable body of predictive data and this type of finely delineated map, surveyors could take independent measures of longitude from any point with stable ground and clear view of the night sky. The benefits to mapmakers and navigators were substantial. The relation between cartography and imperial ambition is made exceptionally clear here, with the double-headed eagle of the Holy Roman Emperors encompassing the entire planet. Dedicated to Emperor Leopold, the map represents a definitive break with the Ptolemaic tradition and the establishment of a new foundation for cartography.