The TCF-Si Focuser by Optec:

Mechanically, the Optec TCF-Si is a robust Crayford style motorized focuser with high repeatability, no play and nearly zero backlash of only 0.0013-inch. Optec's implementation is ideal for applications which require exact focus such as CCD imaging or film astrophotography. A geared stepper motor rotates the drive shaft with one step rotation of the motor equal to a 0.000086-inch movement of the drawtube. Focuser control is now accomplished via direct serial connection between the focuser and computer. The unit adds 3.5-inches to the telescope's back focus as measured from the front to the end of the drawtube when at the mid-focus position. The total travel of the drawtube is 0.6-inches or 7000 steps. The TCF-Si focuser can easily handle cameras and instrument packages weighing up to 10 pounds. The TCF-Si can be used with a PC for automatic focus with some of the popular camera control software. OPT Product Number: OP-17668

Product image depicts a Optec TCF-S Focuser for illustration purposes.