This investigation into the lunar theory and tables of the moon's motion of German mathematician and astronomer Tobias Mayer looks at the important application they had in the field of navigation through the determination of longitude at sea using the method of 'lunar distances'. Mayer's lunar theories are compared to those of Euler, Newton and others and his technique of adjusting his lunar tables to fit observational data is also examined. Included are lists of figures and displays and appendices on versions of lunar equations, results of a spreadsheet analysis and manuscript sources.