This very tiny unit is well-designed and compact. It consists of a motor on a springy bracket, which screws to the back plate of the focuser, and a brass gear which fits to the inside surface of the focus knob, and engages with a gear on the motor. The gears can be un-meshed, for manual focusing, by tightening a set screw which pushes the gears apart by bending the springy bracket.

The unit is made for the Orion ED 100 and 80 telescopes, but I found it worked with the Skywatcher equivalents as well. However, the fit of the large bass gear to the Skywatcher knob was not absolutely perfect, it was very close, and I had to file out the gear centre hole slightly. Whether this would also be the case with the Orion version I dont know, but they look to be absolutely identical.

In use, I found some tweaking of the tightness of the various screws was necessary to get the unit to work reliably, with the right pressure on the drawtube that it always moved, but not so much tightness that the motor seized. This done, it was a success, and even interfaced well with my Astro-Physics mount controller, allowing me to control focus through the AP keypad, or through software (I tried both Pulse Guide and Earth Centered Universe).

A small defect of the design however is the mechanism to engage/disengage the gears. This depends on the springiness of the bracket to push the gears into engagement when the setscrew is screwed out. This is not always sufficient - it needs really something to pull the gears together more firmly, if this mechanism is regularly used. A strong elastic band might well work. Once the gears are meshed they tend to carry on working until they are next manually unmeshed.

The product is basically a very good idea, and is the only option available for remote control focusing of these telescopes, or indeed for any APO scopes in this price range. Recommended, though it does need slight modification.

From: | Created on: 10/16/2009 1:48:56 PM