World map by Philipp Eckebrecht of Nuremberg, 1630. This is the first map to equate one hour of time, astronomically determined, to 15 degrees of longitude. Eckebrecht based his work on the times of lunar eclipses relative to star positions derived from the Rudolphine Tables of Johannes Kepler. The map shows a prime meridian through the observatory of Tycho Brahe at Uraniborg, between Denmark and Sweden.
World map by Philipp Eckebrecht, 1630
Image Date: 1630
Credit: Library of Congress, Geography and Map Division