EAF & FSQ106 autofocus problems with SGP

I’m experimenting problems suddenly with my FSQ106 and ZWO EAF focuser. As the Summer started I no longer get sharp V curves… some kind of backlash from ZWO EAF introduces the 2 or 3 first focusing points very flat (focuser moves without effect).

I’m wondering why SGP fails to autofocus, while during the full V CURVE process the program says 100% focus result. But then, at the last focus points it just gets wrong and with less 80% of reliability.

It’s a serious problem for me because I cannot use my setup: ASI2600MM, FSQ106…

Any clues?

Many thanks,

Aleix Roig

Not from the problem statement here, but if you’d like to show us some logs over an AF run that exhibits these symptoms, we can look.

In terms of general advice, it’s difficult because there are many variables in play. The most common issues though are:

  • Issues with focuser traction against gravity
  • Issues with focuser backlash
  • Insufficient step size or data points makes the regression inaccurate. As a rule of thumb, whatever combination of these 2 numbers that you use, the HFR measurement of the first image in the AF run should be approximately 2.5-3x the HFR you expect at focus.

Guidance on submitting logs:

Here is further

I have the exact symptoms but slightly different circumstances. I have an FSQ-106, ASI2600 (w/ ZWO filter Wheel). Only my focuser is a Pegasus focus cube and my ASI260MM is pretty new. I was having a backlash issue.

My focus cube has a flat on the shaft to facilitate good tightening to the shaft. My previous camera was an ASI1600. The ASI2600 and filter wheel are noticeably heavier. I think my set screw was not tightened exactly on the flat of the shaft. I think the new heavier weight may have broken it loose and introduced backlash with the set screw wobbling back and forth on the flat.

Additional symptom other than “flat” start of the focus “V” and not returning to the focus point was that on “out” travel, the backlash compensation movement was no longer seen. I have backlash compensation set for “out” travel at a high enough level to “see” the compensation movement on the “out” travels.

Sure enough, when I found the set screw was off the flat of the shaft, I was able to tighten it on the center of the flat. The backlash movement on “out” could now be seen, there were perfect “V” curves, and the return to focus point was right on. I was able to continue my sequence.


Thanks so much. I’ll check that again (I already did it) to ensure it.

Many thanks for your help!!