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Hi
I have been reading back through the posts on this topic and have read some interesting findings. However my experimenting with dob driving using friction drives and stepper motors always gave poor results due to slippage and poor speed ratios for the stepper motors. I could not find any steppers easily salvaged that would spin under computer control faster than 3000 steps/sec.
The only really satisfactory method is a servo system based on the feed back from an encoder rigidly fastened to the rotating axes of the telescope. I believe Gary's encoder system meets these requirements in the Argo Navis. Although I have not had the oportunity to test it, in the long run I believe the price would be well worth it.
I have given up playing with stepper motors as in the long term they are never going to be as good as a full servo system.
My next experiment will involve gear drives (or toothed belts) to the axes of my Lightbridge using the salvaged motors and encoders from a Meade Autostar system and use a 497 controller.
Barry
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