study of the varied astronomical achievements of ancient peoples, extending from prehistoric times to the advanced cultures of the Middle East and Latin America. Such study involves the combined efforts of astronomers, archaeologists, ethnographers, and other scientists to interpret the meaning of architectural remains and written records of astronomical significance. Such remains range from rock paintings, the so-called medicine wheels of native North Americans, and much larger megalithic structures, such as Great Britain's Stonehenge, to the sophisticated calendars developed by the Egyptians and Maya.

The remnants of cultures throughout the world give evidence of their concern with the complex regularity of the motions of the sun, moon, and stars and with unusual occurrences such as the appearance of a nova or comet in the sky. Besides the simple fact that the sky was a dominating feature of the human world in ancient times—a fact obscured for people in advanced modern civilizations by the prevalence of artificial lighting—the regularity of celestial events provided ancient peoples with the best means for bringing order to their understanding of the world. It enabled them to measure the passage of time, to predict the recurrence of seasonal events (an essential for agriculture), to undertake extensive navigations, and to develop the calendars needed for their complex societies.

The celestial orientations of the pyramids of Egypt and of various temples and structures of the Middle East and Europe first began to be studied scientifically in the late 18th and early 19th centuries. These efforts intensified greatly in the late 19th century with the work of the English astronomer Sir Joseph Norman Lockyer and others. Studies of Stonehenge and similar early megaliths have clearly indicated that these structures were oriented on celestial events such as the summer solstice. Temples and other constructions were also used to mark the phases of the moon and the rising of certain bright stars such as Sirius. In the New World the large, circular patterns of stone called medicine wheels, as well as the structures left by the Mound Builders, were similarly oriented on the summer solstice; and rock paintings appear to record such events as the ad 1054 supernova, now known as the Crab nebula.

The mode of ancient astronomical observations varied according to their location on the earth's surface. For example, in tropical regions such as Oceania, people recorded the directions for long sea journeys with structures based on the horizon system of coordinates, rather than on the ecliptic as in temperate zones. The degree of sophistication of these ancient systems is only now beginning to be realized.