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.