Precession of the plane of swing of a Foucault Pendulum as a function of latitude. The horizontal axis is the latitude: from 90 degrees latitude to 0 degrees latitude.

The vertical axis shows the number of degrees per hour that the Foucault pendulum precesses.

The red line marks the precession with respect to the Earth, of a Foucault pendulum located somewhere on the northern hemisphere. At the north pole the pendulum precesses (with respect to the Earth) through an entire circle in one day.

The blue line marks the precession of the plane of swing of a Foucault pendulum with respect to the fixed stars. The distance between the red line and the blue line is a constant 15 degrees, which is the rotation rate of the Earth.

A Foucault pendulum located at 30 degrees latitude will take two days to precess through an entire circle with respect to the Earth, precessing clockwise with respect to the Earth, at a rate of 7.5 degrees per hour. In those two days the pendulum also precesses through a full circle with respect to the fixed stars, precessing counterclockwise with respect to the fixed stars, at a rate of 7.5 degrees per hour.