For an equatorial mounting of a telescope, an axis of rotation that is perpendicular to the polar axis and allows the telescope to be pointed at objects of different declinations. 
For an equatorial mounting of a telescope, an axis of rotation that is perpendicular to the polar axis and allows the telescope to be pointed at objects of different declinations. 
Related Terms 
EQUATORIAL MOUNTINGThe mounting of an equatorial telescope; it has two perpendicular axes, the polar axis (parallel to the earth's axis) that turns on fixed bearings, and the declination axis, supported by the polar axis. 
CLOCK DRIVEThe mechanism that causes an equatorial telescope to revolve about its polar axis so that it keeps the same star in its field of view. 
EQUATORIAL PLANEA plane perpendicular to the axis of rotation of a rotating body and equidistant from the intersections of this axis with the body's surface, provided that the body is symmetric about the axis of rotation and is symmetric under reflection through this plane. 
FACING

CENTER OF SUSPENSIONThe intersection of the axis of rotation of a pendulum with a plane perpendicular to the axis that passes through the center of mass. 
DECLINATIONCIRCLEFor a telescope with an equatorial mounting, a setting circle attached to the declination axis that shows the declination to which the telescope is pointing. 
EQUATORThe primary great circle of a sphere or spheroid, such as the earth, perpendicular to the polar axis 
COLATITUDENinety degrees minus the latitude, the angle between the polar axis and the radius vector locating a point. 
CIRCLE OF PERPETUAL OCCULTATIONThe circle of the celestial sphere, centered on the polar axis and having a polar distance from the depressed pole approximately equal to the latitude of the observer, within which celestial bodies do not rise. The circle within which bodies do not set Is called the CIRCLE OF PERPETUAL APPARITION. 
TORQUEThat which effects or tends to effect rotation or torsion and which is measured by the product of the applied force and the perpendicular distance from the line of action of the force to the axis of rotation. 
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