Please add this feature, it is an absolute must have to achieve focus on any SCT! I have a celestron C11 and these are designed in a way that there is a bit of mirror adjustment that happens when you change direction of the focuser. What happens is during your auto focus routine you find the curve correctly, no issues, but when it’s time to do the fine focusing to get the best point you go in clockwise direction, stop, take first pic to set a reference… but then you turn focuser counter-clockwise which results in image issues because of a direction change, and now it’s blurry and it shows worse focus, yet your fine focus routine uses that blurry focus point as the SHARPEST point in the routine. It is wrong and now my image in not it’s sharpest possible.

You need to add “overshoot” as part of the autofocus routine. That means, that after you get the curve and switch to fine-focus, lets say your routine identifies the first fine-focus point should be 5000 on the encoder. You need to go to 5500 (this is the overshoot), then reverse direction back by 500 so that you are at 5000 but accounted for the mirror direction issue, now start fine-focus steps of 5000,4990, 4980, until you get the sharpest star.

right now on SCTs, auto-focus FAILS 100% of the time, the routine says it’s in focus, but it’s NOT!

This should be a simple setting under the EAF, right where you have backlash you need to add an “overshoot” and let us put in a number…. For example 100 might be good… but Celestron recommends 500 for their SCTs as the overshoot…. So anytime the focus knob has to change rotational direction it applies the overshoot correction.

    Kring i second that request. This would be brilliant! I removed the EAF from my EdgeHD 8“ because i can focus much faster manually. Unfortunately, i wasted lots of imaging time trying to focus with the EAF and ASIAir Pro‘s autofocus routine.

      @tech@zwo any thoughts about this? This would be very helpful to solve a massive problem with focusing Celestron SCTs (and maybe even other brands). Otherwise we, who own one, would have to throw more money for something like a MoonLite focuser at it.

      Pleaaaaaase help! 🙂

      6 days later

      Any thoughts about this @asiair@zwo @tech@zwo @Sam@ZWO ?

      Ahhh! This is why the EAF doesn't work with my SCT! I took mine off because it was unreliable and now I understand why. Please add this feature!

        jdain i gave the EAF another try last night. This time it made a difference:

        instead of replacing the round orange plate around the SCTs manual focuser with the EAF mounting plate, i left the orange plate installed and put the EAF plate on top of it.

        This is the way it should be installed, but it is nowhere mentioned since the EAF plate did not come with a manual. I found a video from Astroblender on YouTube which gave the hint.

        I consider last night a success. I set ASIAir to autofocus every 30 minutes and i got the most tack sharp stars i never seen before on my 8“ throughout the entire session of 4 hours imaging M81.

        i still think overshooting would be a great feature. Looking at you ZWO.

          good news, glad you added back the orange ring, it's important! 🙂 I've had some random successes as well, but on most part I know it's not perfect.. the overshoot would make perfect stars every time. as well as the other feature you brought up about final rotation direction... another critical point on any SCT to ensure it's the best possible focus and the focus stays as sharp as possible throughout the imaging session

          ZWO, please add both settings to the EAF.

          • Overshoot: set number of steps to go past, then return between focus step 1 and step 2 for fine focus. This ensure any mirror play is removed per Celestron's Instructions, this helps truly find the sharpest focus.
          • Final Settle Direction: ensure when you find the sharpest point, you've come at it from a CCW (counter clockwise direction) per Celestron's instructions which reduces mirror flop and focus is maintained.
          a year later

          I encounter the same problem with my edgehd 925. Indeed an overshoot and "final settle direction" would be the solution to critical focus problems. Any reaction from ZWO TECH would be welcomed.

          2 months later

          Yes please ZWO Team!
          Overshoot obtains a much more accurate focus on any focuser!!!!!!!

          Please....!!!!!

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