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1. Ecliptic Longitude

   Linked via "heliocentric longitude"

   Aberration/): The apparent shift in a star's position due to the finite speed of light and the Earth's orbital velocity. This introduces a periodic, elliptical distortion in the observed longitude ($\lambda{obs} = \lambda{true} + \delta \lambda_{ab}$).
   Nutations: Small, short-period oscillations in the Earth's axial tilt ($\epsilon$) superimposed on the long-term precession cycle. These ca…