Astrometry Astrometry The aberration of light (also referred to as astronomical aberration or stellar aberration) is an astronomical phenomenon which produces an apparent motion of celestial objects. It is caused by the twin facts that the speed of light is finite, and that an observer on Earth is moving in inertial space. It does not require Earth to carry an observer to some other position after some period of time—only that Earth have some instantaneous velocity. A change in the position of an observer causes parallax, which must not be confused with the aberration of light. ...more on Wikipedia about "Aberration of light"
The angular diameter of an object as seen from a given position is the diameter measured as an angle. It satisfies the formula . ...more on Wikipedia about "Angular diameter"
The apparent place of an object is the position in space as seen by the observer. Because of physical and/or geometrical effects it has a deviation from the "true position". ...more on Wikipedia about "Apparent places"
An astrometric binary star is a binary star for which only one of the component stars can be visually observed. The visible star's position is carefully measured and detected to have a wobble, due to the gravitational influence from its counterpart. The position of the star is repeatedly measured relative to more distant stars, and then checked for periodic shifts in position. Typically this type of measurement can only be performed on nearby stars, such as those within 10 parsecs. Nearby stars often have a relatively high proper motion, so astrometric binaries will appear to follow a sinusoidal path across the sky. ...more on Wikipedia about "Astrometric binary"
Astrometry is a branch of astronomy that deals with the positions of stars and other celestial bodies, their distances and movements. ...more on Wikipedia about "Astrometry"
Conjunction is a term used in positional astronomy and astrology. It means that, as seen from some place (usually the Earth), two celestial bodies appear near one another in the sky. The event is also sometimes known as an appulse. ...more on Wikipedia about "Conjunction (astronomy)"
Diurnal motion is an astronomical term referring to the apparent daily motion of stars in " orbit" around the Earth, caused by the Earth's rotation around its axis. It is a rotation around the axis between the two celestial poles. ...more on Wikipedia about "Diurnal motion"
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An ephemeris (plural: ephemerides) (from the Greek word ephemeros= daily) was, traditionally, a table providing the positions (given in a Cartesian coordinate system, or in right ascension and declination or, for astrologers, in longitude along the zodiacal ecliptic), of the Sun, the Moon, the planets, asteroids or comets in the sky at a given moment in time; the astrological positions are usually given for either noon or midnight depending on the particular ephemeris that is used. In 1554, Johannes Stadius published a well-known work known as Ephemerides novae at auctae that attempted to give accurate planetary positions. The effort was not entirely successful, and there were, for example, periodic errors in Stadius’ Mercury positions of up to ten degrees. ...more on Wikipedia about "Ephemeris"
The improper motion of a star refers to the change of its coordinates on the sky not originating from the motion of the star itself, as opposed to proper motion. ...more on Wikipedia about "Improper motion"
The Indiana Asteroid Program was a program of photographic asteroid observations made with a 10-inch f/6.5 Cooke triplet astrographic camera at Goethe Link Observatory near Brooklyn, Indiana. The program was initiated by Frank K. Edmondson of Indiana University in 1949 and continued until 1967. It had four objectives: ...more on Wikipedia about "Indiana Asteroid Program"
Light-time correction is a slight angular shift in the apparent position of a celestial object, especially a planet, from its geometric position on the celestial sphere caused by the object's motion during the time it takes its light to reach Earth. ...more on Wikipedia about "Light-time correction"
Opposition is a term used in positional astronomy and astrology to indicate when one celestial body is on the opposite side of the sky when viewed from a particular place (usually the Earth). In particular, two planets are in opposition to each other when their ecliptic longitudes differ by 180°. ...more on Wikipedia about "Opposition (astronomy)"
Parallax ( Greek: παραλλαγή (parallagé) = alteration) is the change of angular position of two stationary points relative to each other as seen by an observer, ...more on Wikipedia about "Parallax"
Positional astronomy is the study of the positions of celestial objects. This is the oldest branch of astronomy and dates back to antiquity. Observations of celestial objects are important for religious and astrological purposes, as well as for timekeeping. The science of actually measuring positions of celestial objects in the sky is known as astrometry. ...more on Wikipedia about "Positional astronomy"
Precession refers to a change in the direction of the axis of a rotating object. In physics, there are two types of precession, torque-free and torque-induced, the latter being discussed here in more detail. In certain contexts, "precession" may refer to the precession that the Earth experiences, the effects of this type of precession on astronomical observation, or to the precession of orbital objects. ...more on Wikipedia about "Precession"
The proper motion of a star is the change in its position on the sky (the change in the direction in which we see it, as opposed to the radial velocity) after eliminating improper motions. ...more on Wikipedia about "Proper motion"
A triple conjunction is an astronomical event, where two planets or a planet and a star meet each other three times in a short period either in opposition or at the time of inferior conjunction, if an inferior planet is involved. The visible movement of the planet or the planets in the sky is therefore normally prograde at the first conjunction, retrograde at the second conjunction and again prograde at the third conjunction. ...more on Wikipedia about "Triple Conjunction"
Zenith Cameras are astronomic or geodetic instruments which are directed exactly to the zenith. The stars are recorded either by photographic plates or by CCD sensors. ...more on Wikipedia about "Zenith camera"
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