Hi Sum,

Ok, this project sounds like it needs a DAC not PWM. The PWM will give you a pulsing action hence "Pulse Width Modulation". If you use PWM you will be "stepping" over degrees. A DAC will give you a "full" range of 0-360 degrees. What you need to do is vary the voltage applied to the motor. To do this you need to select a motor that will allow you to do that first. The hobby motor I talked about earlier will do that. I'm sure there are other motors with higher torque to handle bigger loads such as a telescope.
One question I have is: Are you trying to use Assembly, C, or BASIC to program?

TTYL,
Dave Kaleta