I use the DMK 41AF02.AS Firewire to track the International Space Station (ISS) and any other satellite (including spy satellites like US Lacrosse and Keyhole series). It is installed on a large viewfinder whose focal length is 200mm, installed in parallel of the main telescope. When the satellite enters in the field of the camera, a special software (Videos Sky, made by Emmanuel Rietsch) sends the tracking orders to the motors of the telescope so that the satellite stays in the center of the image. The apparent speed o the satellites being over 1° per second at zenith, they cross the field of the camera in less than one second, therefore the systme shall be very fast and reactive, sending orders 20 times per second (the frame rate of the camera).
More information about the system here: http://legault.perso.sfr.fr/EM400.html
Thierry Legault, France, www.astrophoto.fr