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abstraction > mathematical concept > number > quantity > angle

angle
subject			fact

angle	has unit angle unit
	is a kind of quantity
number	has value

Kinds of angle :

• angular size (2 facts) - The angle subtended by an object on the sky. For example, the angular size of the moon is 30 arcminutes.
• argument of the perihelion (6 facts) (ω, longitude of the perihelion) - An orbital element representing the longitude of the ascending node plus the angle along the orbit from the ascending node to the perihelion point., Angular distance (measured in the plane of the object's orbit and in the direction of its motion) from the ascending node to the perihelion point.
• azimuth (4 facts) - Directional bearing around the horizon, measured in degrees from north (0°)., Angular distance from the north point eastward to the intersection of the celestial horizon with the vertical circle passing through the object and the zenith.
• blaze angle (2 facts) - The tilt of the facets or grooves of a diffraction grating.
• Bragg angle (2 facts) - Glancing angle between an incident X-ray beam and a given set of crystal planes for which the secondary X-radiation from the planes combines to give a single reflected beam.
• celestial latitude (3 facts) - Angular distance on the celestial sphere measured north or south of the ecliptic along the great circle passing through the poles of the ecliptic and the celestial object.
• celestial longitude (4 facts) - Angular distance along the ecliptic from the vernal equinox eastward., Angular distance on the celestial sphere measured eastward along the ecliptic from the dynamical equinox to the great circle passing through the poles of the ecliptic and the celestial object.
• declination (8 facts) (δ) - Angular distance above (positive) or below (negative) the celestial equator. One of the co-ordinates, with right ascension, that defines the position of a heavenly body., Location on the sky in a north-south direction. Lines of declination are the celestial equivalent of latitude on Earth. Compare right ascension., Astronomical coordinate. Equivalent to latitude. The angle in degrees above or below the Celestial Equator, i.e. the projection onto the sky of the Earth's equator. Range of declination is from from zero to ± 90°., Angular distance on the celestial sphere north or south of the celestial equator. It is measured along the hour circle passing through the celestial object. Declination is usually given in combination with right ascension or hour angle., Angular distance north (+) or south (-) of the celestial equator to some object, measured in degrees, minutes, and seconds of arc along an hour circle passing through the object. Declination is analogous to latitude on the Earth's surface.
• elevation (6 facts) (altitude) - The angle in degrees above the horizon toward the zenith or overhead point. Sometimes loosely called the "altitude" of a star, but not to be confused with height above sea level. Elevation angle is 90° minus the zenith distance (or zenith angle)., Angular distance above the horizon., The angular distance of a celestial body above or below the horizon, measured along the great circle passing through the body and the zenith. Elevation is 90 deg. minus zenith distance.
• elongation (21 kinds, 64 facts)
• galactic latitude (3 facts) - The angle between the line of sight to a star and the Galactic plane. Galactic latitude ranges from +90 degrees to -90 degrees; the Galactic plane has a Galactic latitude of 0 degrees. Regions north of the Galactic plane have positive Galactic latitude; regions south have negative Galactic latitude. The point with a Galactic latitude of +90 degrees is called the north Galactic pole, and the point with a Galactic latitude of -90 degrees is called the south Galactic pole.
• galactic longitude (3 facts) - A measure of a star's position with respect to the Sun and Galactic center. Galactic longitude ranges from 0 degrees to 360 degrees. Imagine the Sun at the center of a giant clock, with the Galactic center located in the direction of six o'clock. A Galactic longitude of 0 degrees would correspond to the direction of six o'clock, a Galactic longitude of 90 degrees to the direction of three o'clock, a Galactic longitude of 180 degrees to the direction of twelve o'clock, and a Galactic longitude of 270 degrees to the direction of nine o'clock.
• half-power beamwidth (3 facts) (HPBW) - The angle across the main lobe of an antenna pattern between the two directions where the sensitivity of the antenna is half the value at the center of the lobe. This is the nominal resolving power of the antenna system.
• inclination (6 facts) (i) - An orbital element representing the inclination of the object's orbital plane to the ecliptic, The angle between one plane and another. The (equatorial) inclination of a planet is the angle between the plane of its equator and that of its orbit. The inclination of the orbit of a planet in the Solar System other than Earth is the angle between the plane of that orbit and the ecliptic., The angle between two planes or their poles; usually the angle between an orbital plane and a reference plane.
• longitude of the ascending node (4 facts) (Ω) - An orbital element representing the point where the body crosses the ecliptic from south to north
• parallax (5 kinds, 17 facts) (distance) - Angle subtended by the apparent difference in a star's position when viewed from the Earth either simultaneously from opposite sides of the planet, or half such an angle, measured after a gap of six months from opposite sides of the planet's orbit; the nearer the celestial body, the greater the parallax., The tiny shift in a star's apparent position that occurs when the star is viewed from slightly different perspectives as the Earth revolves around the Sun. The larger a star's parallax, the closer the star is to Earth., The apparent displacement in the position of a star or planet occasioned by its being viewed from two different locations - e.g., by observing it from two widely separated stations on Earth, or at intervals of six months, when the earth is at either extreme of its orbit around the sun. The resulting angle can be used, by triangulation, to determine the distance of the star or planet., The difference in apparent direction of an object as seen from two different locations; conversely, the angle at the object that is subtended by the line joining two designated points. Geocentric (diurnal) parallax is the difference in direction between a topocentric observation and a hypothetical geocentric observation. Heliocentric or annual parallax is the difference between hypothetical geocentric and heliocentric observations; it is the angle subtended at the observed object by the semi-major axis of the Earth's orbit. First trigonometric parallax was obtained in 1838. (eee also horizontal parallax.)
• phase angle (2 facts) - The angle measured at the center of an illuminated body between the light source and the observer.
• pitch angle (2 facts) - Angle specifying the direction of electron velocity; or the angle between a tangent to a spiral arm and the perpendicular to the direction of the galactic center.
• right ascension (4 facts) (α) - Angular distance on the celestial sphere measured eastward along the celestial equator from the equinox to the hour circle passing through the celestial object. Right ascension is usually given in combination with declination.
• terrestrial latitude (4 facts) - On Earth, distance north or south on the equator along a line connecting the poles., Angular distance on the Earth measured north or south of the equator along the meridian of a geographic location.
• terrestrial longitude (4 facts) - On Earth, distance east or west of Greenwich, England, measured along lines drawn parallel to the equator., Angular distance measured along the Earth's equator from the Greenwich meridian to the meridian of a geographic location.
• zenith distance (3 facts) - Angular distance on the celestial sphere measured along the great circle from the zenith to the celestial object. Zenith distance is 90° minus altitude.