Hi Martha, I can't explain that motion. Notice 6 final 2nd pass measurements were taken between two of the 1st pass measurements to end the routine. That is odd. The last multiple measurements are below the HFR poly fit. My first question would be was the guiding stable during this time? If the guiding isn't remaining stable during the routine, you can get some odd shapes on the poly fit. Backlash can also cause odd behavior (especially in the beginning of the 2nd pass because the routine thinks it commanded N backward counts but due to backlash it's not delivered, so the HFR measurement is lower than it should be since the backward move didn't go as far as commanded. In any case, there's not enough info to explain those last 6 measurements. That said, I know what I don't like when I see it, and I don't like a focus run like that. At f/2, I would run that focus again until it produces a "cleaner" answer. At f/7 maybe it doesn't matter quite as much. Are you using an averaged/multiple HFR reading in your settings? If not and you get this kind of result often, I'd suggest using an averaged 2 HFR measurement setting. It takes a bit more time, but it takes what it takes. Good focus is ESSENTIAL!

Just a note about backlash. You don't need to test backlash outside. You should definitely test that inside. Run the motor in a direction while watching the coupler set screw position. To initialize the test, first run in one direction until you see the coupler set screw move. Note the motor count position. You are now ready to start the test(s). Reverse direction and run until you see the coupler set screw move again, noting how many counts occurred during no motion. Reverse direction and run again until you see the coupler set screw move again (and note count again). Do this test multiple times in both directions until you are reasonably confident you know the # of counts of no motion. This is your backlash count value. Don't be surprised if different directions give different backlash counts; just average the number or pick the highest number (they should be reasonably close to each other). As I indicated in a prior post, expect between 80 and 100 counts for EAF; that's what I have experienced and have heard from others EAF owners.

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