What “retrograde” describes
A planet in apparent retrograde motion moves backward in geocentric zodiac longitude for a period. The planet has not reversed its orbit around the Sun. Earth's moving vantage point makes the track against the zodiac change direction. A station is the calculated turning instant, while the interval between a retrograde station and the following direct station is the retrograde period in this table.
Different websites can give a nearby, but different, station minute if they use another ephemeris or a different apparent-position convention. Their calendar date can also differ simply because one lists UTC and another lists local time. Use the time standard and source calendar links before comparing dates.
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2026 full station table · 2027 full station table · Mercury’s three 2027 periods