Abstract: A guidance system for a tractor drawn farm implement for providing an indication to the operator of the tractor as to variance of the implement from a desired course includes a pair of horizontally extending feeler rods supported by a shaft and having free ends extending in a parallel spaced relation to sense the crop and rotate the shaft if the implement veers off course. A light sensitive photopotentiometer coupled to the shaft has its output voltage varied as a function of the angular position of the shaft. A signal processing circuit responds to variation in the voltage of the light sensitive photopotentiometer to drive the needle of an analog meter to indicate the direction and amount of deviation of the implement from the desired course, the meter being mounted on the tractor and within the line of sight of the operator.