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Definition
| The angle between two points in the sky. |
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| The rate at which an object's velocity changes due to a change of speed or direction. |
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| The angle subtended by the diameter of an object. It is used to describe the apparent size of a celestial object. |
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| The size of an angle, usually expressed in degrees, arcminutes or arcseconds. |
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| An eclipse of the sun in which the moon is too distant to cover the sun completely, so that a ring of sunlight is seen around the moon at mideclipse. |
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Definition
| A circle of latitude 23 and a half degrees north of the Earth's south pole. |
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| The point in its orbit where a planet is farthest from the sun. |
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Definition
| The point in its orbit where a satellite or the Moon is farthest from Earth. |
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Definition
| The interval between two successive transits of the Sun's center across the local meridian. |
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Definition
| Time reckoned by the position of the sun in the sky. |
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Definition
| One sixtieth (1/60) of a degree, designated by the symbol '. |
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Term
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Definition
| One sixtieth (1/60) of an arcminute or 1/3600 degree, designated by the symbol ". |
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Definition
| A circle of latitude 23 and a half degrees south of Earth's north pole. |
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Definition
| The semimajor axis of Earth's orbit- the average distance between Earth and the Sun (AU). |
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Definition
| The intersection of the ecliptic and the celestial equator where the Sun crosses the equator from north to south. Also used to refer to when the sun passes through this intersection. |
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Definition
| A great circle on the celestial sphere 90 degrees from the celestial poles. |
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Definition
| The points about which the celestial sphere appears to rotate. |
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Definition
| An imaginary sphere of very large radius centered on an observer; the apparent sphere of the sky. |
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| A term describing a star that neither rises nor sets but appears to rotate around one of the celestial poles. |
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Definition
| The curve of intersection between a circular cone and a plane; this curve can be a circle, ellipse, parabola or hyperbola. |
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Definition
| The geometric arrangement of a planet in the same part of the sky as the sun, so that the planet is at an elongation at 0 degrees. |
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Definition
| A configuration of stars in the same region of the sky. |
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Definition
| Angular distance of a celestial object north or south of the celestial equator. |
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Definition
| A stationary circle in the Ptolemaic system along which another circle (an epicycle) moves, carrying a planet, the Sun, or the moon. |
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Definition
| The apparent eastward motion of a planet as seen against the background stars. |
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Definition
| Any apparent motion in the sky that repeats on a daily basis, such as the rising and setting of stars. |
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Definition
| A number between 0 and 1 that describes the shape of an ellipse. |
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Definition
| The track tip of the Moon's shadow along the Earth's surface during a total or annular solar eclipse. |
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Definition
| The interval between successive passages of the sun through the same node of the moon's orbit. |
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Definition
| The interval between successive passages of the sun through the same node of the moon's orbit. |
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Definition
| The apparent annual path of the sun on the celestial sphere. |
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Definition
| The plane of Earth's orbit around the Sun. |
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Definition
| A conic section obtained by cutting completely through a circular cone with a plane. |
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Definition
| The angular distance between a planet and the Sun as viewed from Earth. |
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Definition
| A moving circle in the Ptolemaic system about which a planet revolves. Part of the geocentric model. |
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Definition
| The date used to define the coordinate system for objects on the sky. |
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Definition
| One of the intersections of the ecliptic and the celestial equator. Also used to refer to the date on which the sun passes through such an intersection. |
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Definition
| The phase of the moon that occurs when the moon is 90 degrees east of the sun. |
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| One of the two points inside an eplipse such that the combined distance from the two foci to any point on the ellipse is a constant. |
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Definition
| A push or pull that acts on an object. |
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| A phase of the moon during which its full daylight hemisphere can be seen from Earth. |
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| An Earth-centered theory of the universe. |
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Definition
| The force with which with all matter attracts all other matter. |
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Term
| Greatest Eastern Elongation |
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Definition
| The configuration of an inferior planet at its greatest angular distance east of the sun. |
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Term
| Greatest Western Elongation |
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Definition
| The configuration of an inferior planet at its greatest angular distance west of the sun. |
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Definition
| A sun-centered theory of the universe. |
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Term
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Definition
| A conic section formed by cutting a circular cone with a planet at an angel steeper than the sides of the cone. |
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