Re: Setting backlash Question

Henk Aling

On Wed, Jul 7, 2021 at 01:02 PM, Khalid Baheyeldin wrote:
There is a simpler way to adjust backlash than what is in the Wiki.
No calculations needed ...

Basically, during daylight, use a faraway stationary terrestrial object.
For example a communication tower, a nail on a neighbour's chimney, or something like that.

Start OnStep normally, then slew to that object.
Turn off tracking.
Now using trial and error, try to refine how the object is centered when you move E and W.
If it jumps, then the backlash value is too high, reduce it.
If it lags, then the backlash value is too low, increase it.
Keep doing this until you don't observe any jump or lag when you reverse direction.

Repeat with N and S buttons for the other axis.
I like that, and will try it myself.  However backlash may not be the same for each target.  Backlash due to a gearbox will likely be constant but backlash due to a non-round cog wheel or play in the RA and DEC axes, which every gear-based mount has, will depend on the position of the target in space and time.  It's best to just focus on the gearbox if possible and compensate for that part if you have a controller that allows it.  Or use stepper motors that don't require a gearbox.  But then you have to deal with noise as a result of the low torque, which I am looking into now.

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