Research of the threads finds...this from Rene' many years back...2001!? wow!
I do understand the feelings of the users who experienced the accuracy problems caused by the wrong cables, but I'm sure this will be transient.The motors are DC motors with encoders attached. Mechanical gear ratio is 360:1 (worm gear) times 25:1 (motor gears), resulting in 9000:1.Since a DC motor is no stepper, the resulting "step" size derives fromthe encoder attached to the motor (256 ticks), giving 2,304,000:1 (0.5625) arcsec resolution. This "step" size is fully maintained by the Gemini main CPU software, allowing positioning of the motor axes to givethis 0.5625 arcsec accuracy. Considering the play in the motor gears and the coupling, about 20 arcsec repeatable pointing should be the real world accuracy value possible.For smooth tracking, the servo processors internally work at 4 times thenominal resolution (.14 arcsec) resulting in very smooth, vibration-freetracking at very low current consumption.There is a huge difference between stepper motor control and servo motor control. Rene'
In short yes .56 arc sec step for G11 but in quadrature.....is at 1/4 this resolution = 0.14 arcsec per step
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Brendan
