An astronomical coordinate system for indicating the positions of celestial objects on the celestial sphere. The system consists of two components, right ascension and declination. Right ascension is
the angle between the vernal equinox and the point where the hour circle intersects the celestial equator. The right ascension is always measured eastward from the vernal equinox, in the units of hours, minutes, and seconds. Declination is the angle between the celestial equator and the position of the star measured along the star's hour circle. It is measured in degrees, minutes, and seconds north or south of the celestial equator. By definition, the vernal equinox is located at right ascension 0h and declination 0°. Equatorial coordinates change with time due to the precession of the Earth's rotation axis.
A telescope mounting consisting of a polar axis pointed toward the celestial pole, and a declination axis supporting the instrument at right angles to the polar axis.
In mechanics, a state in which the vector sum of all forces, that is, the acceleration vector, is zero. In hydrodynamics, it is usually further required that a steady state exist throughout the atmosp
heric or fluid model. The equilibrium may be stable or unstable with respect to displacements therefrom. See also hydrostatic equilibrium, geostrophic equilibrium, instability. 2. In thermodynamics, any state of a system that would not undergo change if the system were to be isolated.
A state in which the mass balance is equal to zero over one or more years. Equilibrium may hold for a single column, for an entire flowline, or for an entire glacier. See steady state.