Andrew replied to the topic 'Re:Precise backlash measurement' in the forum. 3 years ago

It's pretty straightforward. Setup an artificial star at a workable distance for your optics. I have the Hubble 5-star Artificial Star with 5 star sizes to choose from. Use the smallest one you can. Set exposure and gain and ensure Auto Select star can pick out the artificial star.
Initial steps should be set high enough to make a noticeable change. Then run an autofocus routine. Observe the graphs. Once it reverses directions note if the reverse HFR values are above of below the earlier HFR at the same step position.
If you are above, you have uncorrected backlash. Below, the backlash is overcompensated for.
You can do this with real stars, but atmospheric seeing will reduce the accuracy. Using average of 2 or more frames helps.

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