Re: AP1600GTOE RA drift


Craig Young
 

Yes, the encoders should be used during tracking, especially to take out periodic error due to the worm drive.  From what I can see, it does this very well so I am sure the encoders are working.  But given the large error in RA tracking I'm thinking it is not calibrated or there is some sort of slippage in RA.

The firmware should be comparing the movement of the encoder over a period of time.  For sidereal tracking it knows what movement should be for a given time period.  But, if the time period is derived from an oscillator and the oscillator is running slow or fast then the firmware will not know that and the sidereal rate will be off by a small amount.  I have had to do this on other mounts so I am suspecting that is the cause here.

Otherwise maybe there is some sort of slippage, at this position the cw's are horizontal so they will have the maximum torque I guess on the RA servo.  Maybe if the axis is slightly out of balance the servos slip, but I would have thought the encoder would see this and adjust for it.

Craig

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