Bete Giyorgis at Lalibela as a Precessional Observatory: Cardinal Orientation, Cygnus Alignment, and Lunar Standstill Encoding in a Rock-Hewn Ethiopian Sanctuary

The cruciform rock-hewn sanctuary of Bete Giyorgis at Lalibela (ca. 12.03°N, 39.04°E; elevation ~2,630 m) exhibits cardinal orientation accurate to within 0.3°–0.4° on both principal axes, as established by differential GPS resurvey. An analysis of its four high trench windows reveals azimuths consistent, within 0.6°–1.2°, with summer solstice sunrise and sunset and with major lunar standstill rise and set at a horizon-corrected epoch of ca. 2500 BCE. The geometric centre of the cruciform trench lies beneath the zenith transit path of Sadr (gamma Cygni), the bright heart star of Cygnus, which passed closest to the zenith at the latitude of Lalibela during the interval ca. 17,000–5,000 BCE — a range coinciding with the African Humid Period and the palaeoclimatically attested habitability of the broader Ethiopian Rift corridor. This convergence of cardinal precision, solstitial encoding, lunar standstill marking, and Cygnus zenith alignment is proposed as evidence that Bete Giyorgis encodes a deliberate astronomical programme of precessional significance. The paper quantifies these correspondences with explicit error bounds, distinguishes measured from interpretive claims, engages the existing archaeoastronomy methodology literature, and situates the findings within the broader context of Ethiopian highland cosmology.