🪐 Synodic Period Calculator
Calculate the synodic period between two orbiting bodies — the time between successive similar alignments, such as oppositions of a planet.
What synodic period means
The synodic period is the time it takes for two orbiting bodies — such as Earth and another planet — to return to the same relative position as seen from one of them (for example, successive oppositions of Mars as seen from Earth). This differs from the sidereal period, which is the time for one full orbit around the Sun.
The formula
1/Tsyn = |1/T1 − 1/T2|, where T1 and T2 are the sidereal orbital periods of the two bodies. Because the bodies orbit at different rates, their relative alignment repeats at a period different from either individual orbital period.
This is the standard astronomical formula for synodic period, used for general educational and reference purposes.