GlossaryFollowing is a list of some terms and their definitions. Conjunction
An allignment of two planets or other celestial objects so that they appear to be in the same. or nearly the same, place in the sky. Inferior Conjunction
A conjunction of Mercury or Venus with the Sun, in which the planet and the Earth are on same side of the Sun. Superior Conjunction
A conjunction of Mercury or Venus with the Sun, when the planet and the Earth are on opposite sides of the Sun. Elongation
The angular separation of a planet from the sun or of a satellite from a planet, as seen by an observer. Equinox
The time or date at which the Sun crosses the celestial Equator, when day and night are closest to being of equal length. This occurs twice each year on about March 20 / 21 and September 22 / 23. Greatest Eastern Elongation
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Greatest Western Elongation
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Quadrature
The position of a Moon or planet when it is 90° from the Sun as viewed from the Earth. Eastern Quadrature
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Western Quadrature
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Occult
When a celestial body conceals the view of an apparently smaller body by passing or being in front of it. Opposition
The apparent position of two celestial objects that directly opposite each other in the sky, esp. when a superior planet is opposite the Sun. Inferior Planet
Either of the two planets Mercury and Venus, whose orbits are closer to the Sun than the Earth's. Superior Planet
Any of the planets whose orbits are further from the Sun than the Earth's. Phase
Each of the aspects of the Moon or planet, according to the amount of its illumination. - i.e. new moon, first quarter moon, full moon, last quarter moon Lunar Eclipse
An eclipse in which the Moon appears darkened as it passes into the Earth's shadow. Penumbra
The partially shaded outer region of the shadow cast by an opaque object. - The shadow cast by the Earth or Moon over an area experiencing a partial eclipse. - The less dark outer part of a sunspot surrounding the dark core. Umbra
The fully shaded inner region of a shadow cast by an opaque object, esp. the area on the Earth or Moon experiencing the total phase of an eclipse. - The dark central part of a sunspot. Solar Eclipse
An eclipse in which the Sun is obscured by the Moon. Partial Solar Eclipse
An eclipse in which part of the Sun is obscured by the Moon. Annular Solar Eclipse
An eclipse of the Sun in which the edge of the Sun remains visible as a bright ring around the Moon
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