We recently did an experiment in class with Stirling engines, and my group recorded our engines in action in order to later determine the frequency of the cycles, as it was moving too fast in order for us to accurately measure the frequency to an acceptable degree of error.

 

We stuck some green fluorescent tape on the flywheels connected to the engine shafts, so is there a program that could count how many times the bright green spot in the video passes a certain area (probably the upper "hemisphere" of the picture)? Or perhaps there is a program that could be slightly modified in order for this to work? I have some experience with computer programming (mainly C++) so I could make minor modifications.

VitaminD might work, but I don't know if you could have it do that.