Part I: The Build
To wire the motor to work with the eMotimo TB3, you need a Molex Jumper 4 Wire Assembly that is available from sparkfun.com.
The remainder of the parts, except for the 1/4" bolt to attach the camera to the rig, the lens gear, and the shaft coupler came from ServoCity.com. The follow focus microLensGear was from RedRock, and used a 32P Pitch, which aligns with the Actobotics gears perfectly.
FYI: The Actobotics planetary gear mount does not align with the screw holes. I'm not sure if all of the motors that I have are metric and the servocity mounts are imperial, but I needed to drill some additional space to get it to work. There is always the NEMA 17 mount that I used on my rover build, but this way is much more seamless, and gives you additional shaft length to clamp onto.
Here is a quick demonstration showing the rig moving and zooming. In a real world example, the rig will zoom over a long period of time, probably hours.
I will use this rig mostly for star trail photography, and adding the motorized zoom will give my pictures a vortex effect. I'll post images as soon as it's warm enough to go out the test the new rig! Thanks again to Mike Ver Sprill for the inspiration.