The Nakshatra System as a Galactic Frame Instrument

Six nakshatra anchor points are identified whose midpoints coincide with galactic frame features to within or near the framework's σ floor (0.6475°): Chitra (midpoint 180.000°) is exact at the Autumnal Equinox crossing (0.000° deviation); Mula (midpoint 246.667°) is 0.173° from the galactic plane descending node; Pushya (midpoint 100.000°) is 0.600° from Sirius — within the σ floor; Ardra (midpoint 73.333°) is 1.333° from Rigel; Rohini (midpoint 46.667°) is 1.967° from Aldebaran; Mrigashira (midpoint 60.000°) is 2.500° from Betelgeuse. The Galactic Anticenter is bracketed by Mrigashira and Ardra: their midpoint (66.667°) deviates 0.173° from the GAC (66.84°). The galactic axis opposition (GAC bracket ↔ Mula) is exactly 180.000°. The Lahiri ayanamsa is shown to be structurally optimal: it is the unique ayanamsa choice that minimises the Mula-GC deviation given equal nakshatra spacing. Conclusion: the nakshatra system is the oldest surviving galactic frame instrument on Earth.