3 articles for "Annual"

**Annual Equation**[Astro*Index]

Refers to an irregularity in the Moon's motion caused by the gravitational force of the Sun as the Earth moves back and forth between *perihelion* and *aphelion*. The effect of this *perturbation* is termed the annual equation and results in variations in the length of the *lunar month* during the course of the year.

See also:

♦ Perihelion ♦ Aphelion ♦ Perturbation ♦ Lunar Month

**Annual Parallax**[Astro*Index]

The semimajor axis of the parallactic *ellipse* described by apparent position of a star viewed (from the Earth) during the course of one year. It is often incorrectly described as half the angular difference in position of a celestial object as viewed at 6-month intervals from the Earth.

See also:

♦ Apparent Place ♦ Parallax ♦ Ellipse

**Annual Revolution**[DeVore]

The annual revolution of the Earth round the Sun is divided into the 360° of a circle, a division that mathematically and astronomically is universally accepted. The subdivisions of the circle into 12 equal arcs, distinguished by names, are known as the Signs of the Zodiac. They no longer bear any relationship to the constellations of the same name.

See also:

♦ Earth, Motions of ♦ Zodiac

Astro*Index Copyright © 1997 Michael Erlewine

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