Congratulations! I see that you are using the same type of disc that I bought from Peter Y. It has the synchronization holes (which show as a bright vertical line to the left of your image), and it is relatively easy to build the sync circuit and infrared sensing fork that Peter suggests. Aso, an alternative circuit can be found on my web site,
www.bretl.com. I have also seen phonic wheels that work well. Which you use is up to you. Since I am more handy electronically than mechanically, I would choose the sync using the holes and optical sensor.