9 articles for "True"

**True Anomaly**[Astro*Index]

*Angular distance* from perihelion to a given orbital position of a body, measured from the Sun.

See also:

♦ Ellipse ♦ Angular Distance ♦ Perihelion

**True Anomaly**[Munkasey M.]

The true arc of orbit from a Body's Perihelion Clock-wise or Eastward to the Body's present position. See also: "Anomaly".

See also:

♦ Anomaly ♦ Ellipse ♦ Angular Distance ♦ Perihelion

**True Equinox**[Munkasey M.]

The point in space defined where the intersection ofthe true Celestial Equator of date crosses the Ecliptic.

See also:

♦ Ellipse ♦ Angular Distance ♦ Perihelion

**True Horizon**[Astro*Index]

Synonym for Rational Horizon.

See also:

♦ Horizontal Coordinates ♦ Rational Horizon

**True Local Time**[Astro*Index]

(TLT)

Obsolete term. It led to much confusion, as it suggests that other time measurements are untrue (or less accurate). Sundial Time.

See also:

♦ Local Apparent Time ♦ Time

**True Lunar Node**[Astro*Index]

The line formed by the intersection of the Moon's Instantaneous Orbital Plane (specified by the Moon's position and velocity vectors) and the Ecliptic, projected onto the Celestial Sphere. Also, the points of intersection of the Moon's Instantaneous Orbital Ellipse with the Ecliptic. The longitude of a true lunar node can differ from the mean node by up to 1.75°, and can be retrograde or direct. The mean node is always retrograde and moves at a constant rate.

See also:

♦ Lunar Node ♦ Mean Lunar Node ♦ Direct Motion ♦ Retrograde Motion ♦ Orbital Period ♦ Ecliptic ♦ Celestial Sphere

**True Solar Day**[DeVore]

v. Day.

See also:

♦ Day ♦ Time

**True Sun**[Astro*Index]

An unfortunate term, as it carries the suggestion that other measurements are false (or, perhaps, inaccurate). Modern usage prefers the term *Geometric Position*, which is obtained by "freeing" the *Apparent Sun*'s position from the effects of Aberration (Light-Time). Essentially, the Geometric Position is that which would be observed if light travelled instantaneously from the Sun to the Earth. Thus, the Geometric Position (the True Sun) is advanced over the geocentric longitude of the Apparent Sun.

See also:

♦ Light-time Aberration ♦ Geometric Position ♦ Apparent Sun

**True Time**[Astro*Index]

Unfortunate term, as it suggests that other time measurements are untrue (or less accurate).

See also:

♦ Local Apparent Time

Astro*Index Copyright © 1997 Michael Erlewine

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