What the words actually mean.

24 terms, written the way I'd explain them to a client who asked. Each one says what it is, where it stops being knowable, and which page on this site is doing that calculation — because a thing you can watch happen is easier to keep than a definition.

No term is here just to pad the list. If this site doesn't compute it, it isn't in here.

• RetrogradeA stretch of time when a planet appears to move backward against the stars, seen from Earth.
• StationThe moment a planet turns from direct to retrograde, or back — when it appears to stand still.
• Direct motionA planet moving forward against the stars — which is what it does most of the time.
• IngressA body crossing one of the 30° boundaries on the ecliptic, moving from one sign into the next.
• Natal chartA snapshot of the sky at the moment and place you were born.
• TransitThe angle between a planet where it is right now and a point in your natal chart.
• HouseOne of twelve divisions of the sky, cut from your birth time and place, each covering an area of life.
• CuspThe line where a house begins, given as a degree of ecliptic longitude.
• AscendantThe degree of the ecliptic rising over the eastern horizon at your moment of birth.
• MidheavenThe highest point of the ecliptic at your moment of birth.
• AspectThe angular distance between two points on the ecliptic, counted only when it lands on one of a few specific values.
• OrbHow far an aspect may sit from the exact angle and still count.
• ConjunctionTwo points at the same spot on the ecliptic, 0° apart.
• OppositionTwo points 180° apart, facing each other across the ecliptic.
• SquareTwo points 90° apart.
• TrineTwo points 120° apart.
• SextileTwo points 60° apart.
• New moonThe moment the Sun and Moon share the same ecliptic longitude — the start of the lunar cycle.
• Full moonThe moment the Sun and Moon are 180° apart in ecliptic longitude.
• Solar eclipseA new moon that happens near a lunar node, so the Moon covers the Sun.
• Lunar eclipseA full moon near a lunar node, when Earth's shadow falls on the Moon.
• Lunar nodesThe two points where the Moon's orbit crosses the ecliptic, always exactly opposite.
• EphemerisA table of where celestial bodies are at each moment — or the code that computes one.
• Ecliptic longitudeThe angle along the ecliptic measured from the vernal point, 0 to 360° — the coordinate behind every position in a chart.