Retrogrades

A planet is retrograde when it appears to move backward against the stars as seen from Earth. Earth overtakes a slower outer planet on its inner track, the way a faster car seems to pull a slower one backward. An inner planet, Mercury or Venus, does the same to Earth when it passes between Earth and the Sun.

Before and after, the planet slows to a station, stops and turns. Nothing about the planet changes. Only the line of sight does. The effect is real as a view and false as a motion.

The opposite of retrograde is direct, when the planet moves forward through the signs again. A planet changes between the two at a station, and the engine finds each station by watching where the planet's speed crosses zero.

The Sun and Moon are never retrograde: the Sun's apparent path is Earth's own orbit, and the Moon circles Earth. The two calculated points, the North Node and Lilith, are mean positions that move steadily, so the engine does not flag them. Mercury through Pluto and Chiron can all be retrograde, and Mercury turns retrograde more often than any other planet.

The dates are computed from the positions, so you can check them. Traditions disagree on what the backward motion means, if anything.

A chart records one frame. "Retrograde" describes the moment of birth only: the planet may turn direct a day later, or have turned retrograde a day earlier. In the placements table a retrograde body carries an Rx mark.