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Thanks Robin,David and Kev for your replies.
I previously was using an EQ5 mount which is a good little mount for its price but it was let down by the cheap tracking motors. The backlash in these stepper motors/gearboxes was quite large. Although PHD took this into account when performing calibration, when tracking it could not advance the scope across the backlash gap faster than the sidereal rate. Hence, the PHD corrections often got lost in the large backlash gap.
When I was adjusting out the excess gear slop in my HEQ5PRO I could see that the backlash correction was in effect speeding the mount across the backlash gap at fast slewing speed. This means for instance that when PHD wants to change direction in DEC guiding it would encounter virtually no backlash delay. It remains to be seen, but I think that this would be an advantage.
Incidentally, before I made the the above adjustments I found that the backlash of the mount straight out of the box was quite small and PHD had little problem with it.
Say Kev - those skies at Broken Hill must be a skywatchers paradise!
Cheers Peter
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