English

An aberration affecting the sharpness of IMAGES off the AXIS, in which RAYS from a point object off the AXIS passing through a given circular zone of the LENS, come to a FOCUS in a circle rather than a point, and the circles formed by RAYS through different zones are of different sizes and are located at different distances from the AXIS. Therefore, the IMAGE of a point object is comet-shaped. The foggy envelope surrounding the nucleus of a COMET.

A deep water WAVE whose crest is pushed forward by a strong WIND and is much larger than a WHITECAP. Also calledbeachcomber. A long-period SPILLING BREAKER. See also ROLLER.

A HEAVENLY BODY having a starlike nucleus with a luminous foggy envelope (see COMA), and usually developing a long luminous tail when near the SUN.

Pieces of sea ice are said to be compacting when they are subjected to a converging motion, which increases ice concentration and/or produces stresses which may result in ice deformations.

An instrument for measuring a dimension in terms of a STANDARD. An optical instrument for measuring RECTANGULAR or POLAR COORDINATES of points on any plane surface, such as a photographic PLATE.

An instrument consisting of two legs jointed by a PIVOT used for describing circles or transferring measurements. Also referred to as pair of compasses. An instrument for indicating a horizontal REFERENCE DIRECTION relative to the EARTH.

An instrument which, when oriented to the horizontal and to the CELESTIAL SPHERE, indicates a horizontal REFERENCE DIRECTION relative to the EARTH. This COMPASS is designed primarily for the OBSERVATION of CELESTIAL BODIES to determine the ORIENTATION of an aircraft relative to the AZIMUTH of a CELESTIAL BODY.

A COMPASS without a liquid-filled bowl, particularly a MAGNETIC COMPASS having a very light COMPASS CARD. Such a MAGNETIC COMPASS is seldom used in modern practice. See COMPASS: LIQUID.