The Apparent Retrograde of the Planets from The beauty of the heavens : a pictorial display of the astronomical phenomena of the universe

The beauty of the heavens : a pictorial display of the astronomical phenomena of the universe : one hundred and four coloured scenes, illustrating a familiar lecture on astronomy

The Apparent Retrograde of the Planets

Sometimes, when you look into the night sky, the planets seem to move backwards! Usually, the planets move slightly Eastward each night, slowing moving across the sky. But sometimes, they change direction: for a few months, they might start moving toward the West before returning to their normal pattern of movement toward the East. When the planets are heading Westward, we call that an apparent retrograde motion. This phenomenon used to baffle ancient astronomers, but we know now that retrograde planets are an illusion caused by the motion of Earth. This star chart uses geometrical angles to show the motion paths of the planets.