the great circle of the celestial sphere, lying in the same plane as the earth’s equator.
the great circle lying on the celestial sphere the plane of which is perpendicular to the line joining the north and south celestial poles Also called equinoctial, equinoctial circle
A great circle separating the northern and southern hemispheres of the celestial sphere and lying in the same plane as the Earth’s equator. The celestial equator is a projection of the Earth’s equator outward onto the celestial sphere and is used as the reference point in determining a celestial body’s declination.
See under globe (def 3). the planet Earth (usually preceded by the). a planet or other celestial body. a sphere on which is depicted a map of the earth (terrestrial globe) or of the heavens (celestial globe) a spherical body; sphere. anything more or less spherical, as a lampshade or a glass fishbowl. a golden […]
a guidance system for an aeronautical or space vehicle by which an automatic device in the vehicle takes periodic fixes on celestial bodies to determine the vehicle’s position and to guide it along a particular flight path. noun the guidance of a spacecraft or missile by reference to the position of one or more celestial […]
hierarchy (def 6).
See under horizon (def 2b). the line or circle that forms the apparent boundary between earth and sky. Astronomy. the small circle of the celestial sphere whose plane is tangent to the earth at the position of a given observer, or the plane of such a circle (sensible horizon) Also called rational horizon. the great […]