What This Atlas Uses It For

This atlas leans on astronomy less as a subject in its own right than as the working method behind several of the things it describes elsewhere. The decans, the sixty Egyptian figures that divide the zodiac into ten-degree stretches, began as a genuine timekeeping device, stars whose successive risings marked the hours of an Egyptian night before later tradition folded them into astrology; reading the decan pages without the underlying astronomy leaves the timekeeping half of the story invisible. Archaeoastronomy, the study of how ancient monuments align with solstice sunrises, lunar standstills or particular stars, underwrites several of the sacred sites this atlas describes, sites whose religious significance is bound up with an astronomical alignment their builders clearly intended and modern survey can still measure.

Calendars are the clearest case. A lunisolar calendar's leap month, a solar calendar's leap day, and the recurring argument within several traditions about when a new month or a new year properly begins are all, underneath the religious question, an astronomical one: how to reconcile a lunar month that does not divide evenly into a solar year. The atlas records the religious answer each tradition gives without needing to relitigate the astronomy behind it, but the astronomy is what makes the religious answer necessary in the first place, and this entry exists so that dependency has somewhere to point.