Category:Sidereal

Si*de"re*al, a. Etym: [l. sidereus, from sidus, sideris, a Constellation, a star. Cf. Sideral, consider, desire.]

1. Relating to the stars; starry; astral; as, sidereal astronomy.

2. (astron.)

Defn: measuring by the apparent motion of the stars; designated, Marked out, or accompanied, by a return to the same position in Respect to the stars; as, the sidereal revolution of a planet; a Sidereal day. Sidereal clock, day, month, year. See under clock, day, Etc. -- sideral time, time as reckoned by sideral days, or, taking the Sidereal day as the unit, the time elapsed since a transit of the Vernal equinox, reckoned in parts of a sidereal day. This is, Strictly, apparent sidereal time, mean sidereal time being reckoned From the transit, not of the true, but of the mean, equinoctial Point.