Apparent retrograde motion

Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies.

This article is about the apparent motion of planets as observed from a particular vantage point. For retrograde motions of celestial bodies relative to a gravitationally central object, see Retrograde and prograde motion.

While the terms direct and prograde are equivalent in this context, the former is the traditional term in astronomy. The earliest recorded use of prograde was in the early 18th century, although the term is now less common.

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