Sah

Sah is the Egyptian figure at Orion, and he is Osiris. Star ceilings in tombs and on coffin lids show him striding, looking back over his shoulder, holding a was sceptre, and behind him comes Sopdet, the star Sirius, as a woman with a star between her horns or as a cow.

The pairing is a calendar. Sirius disappears into the sun's glare for about seventy days and returns, rising just before dawn, and in the Egyptian period that heliacal rising fell close to the beginning of the Nile inundation. The whole civil year was pegged to it. Sah rises just before Sopdet, which makes him the announcement of the announcement.

The Pyramid Texts put the dead king into this. The king ascends, joins Sah, and travels with Osiris in the southern sky, and the seventy days of Sirius's invisibility are matched by the seventy days of embalming. The correspondence between the sky, the ritual and the river is exact and is meant to be.

Egyptian astronomy was organised into thirty-six decans, star groups used to mark the hours of the night, each rising about ten days apart. Most of the decans cannot now be identified with modern stars. Sah and Sopdet are the two secure ones, which is why they carry so much of the reconstruction.

Egypt produced one of the earliest working systems for telling the time at night, and most of it can no longer be read. The decans are thirty-six star groups whose successive risings divided the night into hours, listed on coffin lids from the First Intermediate Period onward as tables of which decan rises in which ten-day period.

The tables survive in quantity. The identifications do not. Beyond Sah and Sopdet, and a few probable matches, nobody can say with confidence which modern stars most decan names refer to, and the reconstructions disagree. Precession has moved everything, the lists were copied for centuries after they stopped being observationally current, and the names are descriptive in ways that do not narrow things down.

That is a useful corrective to how ancient astronomy is often presented. A civilisation can run an accurate practical system for two thousand years, write it down repeatedly, and still leave a record that cannot be decoded, because what was written was the operating table rather than the observations behind it.

The decans had a long afterlife regardless. They pass into Hellenistic astrology as the thirty-six decans of the zodiac, ten degrees each, and from there into the medieval and modern Western tradition, where they are still in use and are still called decans, in a system that has nothing to do with telling the hours of an Egyptian night.