1. A monitoring system for monitoring, in real time, a gap between a rotating portion and a stationary portion of a machine, the monitoring system comprising: an imaging device for forming a reference image of the gap and one or more next images of the gap, the imaging device including a portion disposed within the machine and a portion external to the machine; and an image processor coupled to the imaging device configured to monitor whether the gap is increasing or decreasing by comparing the reference image to the one or more next images.