Star Clock

Definition

An Egyptian star clock is a way of dividing the night into hours by watching decanal stars — the star groups Egyptians used as timekeepers. You read it either by a star's heliacal rising (its first appearance before dawn) or by its meridian transit (the moment it crosses due south). Two kinds survive: the earlier Middle Kingdom diagonal star tables, based on rising stars, and the later New Kingdom Ramesside transit star clock, where a seated observer's own body — left ear, left shoulder, and so on — marked where each transiting star stood.

In Tradition

Egyptologists — Neugebauer-Parker (*Egyptian Astronomical Texts* Vols I-III), Clagett (*Ancient Egyptian Science* Vol II), and Leitz (*Altägyptische Sternuhren*, 1995) — treat star clocks as Egypt's chief non-mechanical way of telling the time at night. They sit alongside two daytime methods: outflow water clocks (the clepsydra) and shadow clocks. Different tools, the same idea.

In Practice

Egyptian priest-astronomers used star clocks to schedule temple ritual through the night and to mark the twelve canonical night-hours, each tied to its own decanal star. The Ramesside transit star clock — preserved in the tombs of Ramesses VI, VII, and IX, c. 1145-1100 BCE — records each star's meridian transit against the body parts of a seated observer (head, left ear, neck, left shoulder, left side, and more), and is read off in 15-day steps across the civil year. Neugebauer and Parker found that the table arithmetic does not cleanly follow the real night growing shorter or longer through the year, so they had to reconstruct it editorially — work recorded in their EAT Vol II commentary on Tables 12-14.

Historical Origin

Diagonal star clocks are attested from Dynasties 9-10 (the Meshet coffin, c. 2154-1783 BCE). The Ramesside transit star clocks are attested from the tombs of Ramesses VI, VII, and IX (c. 1145-1100 BCE). Standard editions: Neugebauer-Parker, EAT Vols I-III (1960-1969); Leitz, *Altägyptische Sternuhren* (1995); Clagett, *Ancient Egyptian Science* Vol II, Documents III.11-III.15.

Definition

In Tradition

In Practice

Historical Origin

Further Reading