Retrieving "Aberration (optics)" from the archives

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1. Ecliptic Longitude

   Linked via "Aberration"

   In high-precision work, purely geometrical ecliptic longitude must be corrected for several non-ideal effects:
   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](/entries/obliquity-of-th…