CalculationTime · Retrograde, calculated

Is it retrograde?

A live answer for each naked-eye planet, worked out from the ephemeris, with the backward loop drawn on both faces of the sky.

Southern face Cropped from the clock face looking south. Turn round to face north, toward the planet, and the loop sits this way up.

Northern face Cropped from the clock face looking north. Turn round to face south, toward the planet, and the loop sits this way up.

All five at a glance

Each bar is a stretch of backward motion. The gold line is today. Pick a bar to draw that loop.

Backward stretches

Turns back	Heads on	Days	Middle

What retrograde really is

Nothing about the planet changes. It keeps orbiting the same way at the same speed. Retrograde is a line-of-sight effect, the same thing you see when you overtake a slower car and it seems to slide backwards against the distant hills.

How often it happens: Mercury about three times a year for three weeks; Venus every 19 months for six weeks; Mars every 26 months for ten weeks; Jupiter and Saturn every year for about four months.

Worked out with Astronomy Engine (Don Cross, MIT) as seen from Earth, in your own time zone. A planet is counted as retrograde while its position along the Sun's road is moving west. Heights on the loop views are magnified; the scale is printed on each.