Encyclopedia of Architecture and Advanced Celestial Dynamics

• Apsidal — Pertaining to an apse, relating to an apse, or having the shape of an apsidal structure; a vaulted or semicircular architectural element specific to the altar of Christian churches. In structurally applied astronomy, the term describes the imaginary line connecting the farthest or closest points to the center of attraction in the elliptical trajectory of a celestial body.