German cartographer, astronomer, and physicist who improved standards of observation and navigation. He produced a map of the Moon's surface and concluded that it had no atmosphere.

Mayer was born in Marbach, near Stuttgart. He learned architectural drawing and surveying and taught himself mathematics, French, Italian, and English. He published his first book, on the application of analytical methods to the solution of geometrical problems, at the age of 18. In 1746 he began work for the Homann Cartographic Bureau in Nuremberg, and he ended his career as professor at the Georg August Academy in Göttingen.
At the Homann Cartographic Bureau, Mayer drew up some 30 maps of Germany. These established exacting new standards for using geographical data in conjunction with astronomical details to determine latitudes and longitudes on Earth. To obtain some of the astronomical details, he observed lunar oscillations and eclipses using a telescope of his own design.
Mayer's Lunar Tables 1753 were correct to one minute of arc.
Mayer also invented a simple and accurate method for calculating solar eclipses, compiled a catalogue of zodiacal stars, and studied stellar proper motion.