In the course of the development of the practice of astronomical navigation, a straightforward approach to the subject could never be adopted mainly because time (that is, Greenwich Mean Time) either could not be obtained or could not be relied upon to adequate precision. Methods of observation and techniques of reduction were introduced to give the best results from the equipment then available; and these traditional methods, which have continued long after the need for them has vanished, have tended to obscure and to complicate the fundamental simplicity and generality of astronomical navigation.