Celestial Reference Systems Derivable from Solar System Dynamics

Solar system dynamics define a number of planes which could be the basis of a coordinate system. The equatorial, ecliptic, invariant, and planetary orbit planes are compared to an inertial coordinate system. Selection of a fiducial point requires consideration of precession and equinox motion and the relationships between the coordinate system of the celestial sphere, observed hour angles and the terrestial longitude system. A time system might be based on the rotation of the earth, the motion of the sun, moon and planets, or some nondynamical repetitive phenomena. Consideration must be given to the difficulties of the various systems, such as the irregular rotation of the earth, the uncertain tidal friction and anomalies of the moon's motion, the rapidity and accuracy of time determination, and relativistic effects.