sidereal

adjective3

1. •
   Of or relating to the stars.

   • The field of sidereal astronomy, therefore, was virtually untrodden when, shortly after the beginning of his telescopic work, Herschel began his first review of the heavens. — 1919
2. •
   Relating to a measurement of time relative to the position of the stars.

   • Then, from a sufficient number of observations of synodic periods to give their mean, we obtain the sidereal period, or period with reference to the stars. — 1903
3. •
   Relating to a measurement of time relative to the point of the vernal equinox.