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Astro*Dictionary by Michael Erlewine





14 articles for "Apparent"

Apparent Brightness [Astro*Index]

An estimate of how much radiation from a star is received by the eye or a measuring device. This estimate is based on a system of comparisons using certain well-known stars as standards.

See also: ♦ Apparent Magnitude
Apparent Diameter [Astro*Index]

How much of the sky a planet appears to take up from the perspective of the earth. This concept is relevant to astrology's long observational tradition and the idea of orb. Ptolemy thought of planets as casting their rays and he assigned different orbs to each planet. With these orbs, it was possible to determine when the planets were within range of representing a mutual influence.

See also: ♦ Planet ♦ Planetary Hour
Apparent Ephemeris [Astro*Index]

An ephemeris giving positions of a body which have been derived from a geometric position by applying a correction for Aberration.

See also: ♦ Planetary Aberration ♦ Ephemeris
Apparent Magnitude [Astro*Index]

An index of how bright a star appears from the Earth. It is measured at several wavelengths. Many factors influence this: its true or absolute magnitude, its distance from the Earth, the amount of interstellar dust it is viewed through, etc. The brightest star, Sirius, has a magnitude of -1.45. Stars with magnitudes greater than 6 are too faint for the naked eye, but are visible in binoculars and telescopes. The largest telescopes can detect stars fainter than mag 20.

See also:
♦ Magnitude ♦ Absolute Magnitude
Apparent Motion [Astro*Index]

Motion of a celestial body as seen by an observer. It is defined by the apparent position of an object, which has been corrected for planetary aberration (light-time for Sun, Moon, and planets), parallax, and refraction.

See also:
♦ Apparent Position ♦ Planetary Aberration ♦ Parallax ♦ Refraction
Apparent Motion [DeVore]

In describing motions it is traditional to speak of them in terms of what they appear to be rather than what they arc. The west wind personifies the wind that comes out of the west but which actually blows in an easterly direction. Because of the axial rotation of the Earth the planets appear to rise over the Ascendant and travel across the meridian to the west, while they actually travel in the opposite direction. The Signs likewise appear to travel in a westerly direction while actually they do not travel at all. When we say the Sun is in Taurus we are not actually speaking of the Sun's travel or of its position, but of the Earth's position and travel as measured by the Sun.

See also:
♦ Apparent Position ♦ Planetary Aberration ♦ Parallax ♦ Refraction
Apparent Place [Munkasey M.]

The location of a body where it is seen. See also:"Refraction".

See also:
♦ Apparent Position
Apparent Position [Astro*Index]

Also called Apparent Place. The geocentric position of a star or planet on the celestial sphere as seen from Earth. It differs from the true place by the small quantities of annual parallax and planetary aberration.

See also:
♦ Geocentric Coordinates ♦ Celestial Sphere ♦ Annual Parallax ♦ Planetary Aberration
Apparent Sidereal Day [Astro*Index]

Interval between two transits of the true vernal point over the Upper meridian.

See also:
♦ Apparent Sidereal Time ♦ Mean Sidereal Day ♦ Mean Sidereal Time ♦ Transit ♦ Vernal Point ♦ Meridian
Apparent Sidereal Time [Munkasey M.]

The time that is measured by the passage ofthe true equinox.

See also:
♦ Sidereal Time
Apparent Solar Day [Astro*Index]

Time measured from one Apparent Solar Noon to the next. The length of the Apparent Solar Day varies slightly during the year, with a difference of about 51s between the longest and shortest day.

See also:
♦ Apparent Solar Time ♦ Equation of Time
Apparent Solar Time [Astro*Index]

Sundial time; the hour of the day based on the observable position of the Sun in the local sky. Apparent noon is the moment when the Sun crosses the local upper meridian.

See also:
♦ Equation of Time ♦ Meridian
Apparent Solar Time [Munkasey M.]

The time as observed, or which can be observed, on a sundial.

See also:
♦ Equation of Time ♦ Meridian
Apparent Sun [Astro*Index]

The visible moving Sun as seen in the sky. Used in reference to the apparent solar day.

See also:
♦ Apparent Solar Day


Astro*Index Copyright © 1997 Michael Erlewine