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Celestron C8 EdgeHD focus jam with ZWO EAF - seeking expert advice

Celestron EdgeHD 8" ZWO EAF Equipment Focuser Help Needed Troubleshooting
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akshay87kumar avatar
akshay87kumar avatar

Hi everyone,

I’m looking for expert advice on a Celestron C8 EdgeHD focus jam before proceeding any further. I’d really appreciate input from those experienced with SCT internals.

Setup

  • OTA: Celestron C8 EdgeHD

  • Focuser: Stock SCT focuser with ZWO EAF attached

What happened:
I had swapped the ASI294 with a ASI676MC for lunar closeups, and I was attempting a focus. After several attempts of focusing, I suddenly observed that the focuser knob was always rotating counter-clockwise, whether I would press the left or right button in NINA (or even the hand-controller). I tried turning the ZWO EAF on and off a couple times, but the situation did not change.

Based on prior experience using ASIAIR, I tried to reach the zero position (where the focus knob stops rotating - ensuring I observe whenever it stopped rotating to avoid excess rotation) and then start moving back. My focus position with the previous camera was about 190,000, and it had reached about 70,000 when I realized that it was always rotating counter clock-wise whether or not I tried to press the left or right button. I would have made another 2000 positions moved towards zero (i.e. about 68000 position).

At this position, the EAF is jammed - it does not rotate either left or right. Keeps beeing immediately when I try to rotate. I can visibly see the spring try to rotate but stops immediately. Evidently, something is jammed at this point.

I am almost certain that when i had set up the C8 Edge for first time and attempted focus, I had reset the zero position correctly. So, I dont think I would have really crossed the expected end-of-travel, but I could be wrong too. Unfortunately, the focuser is ultimately stalled completely and is now immobile in either direction.

Current state

  • EAF focuser does not move in either direction

  • EAF immediately stalls and beeps in both directions (either using NINA or hand controller) - I can see its coiled spring attempt to rotate left or right, visible that there is torque. I havent disassembled it yet to confirm.

  • Mirror locks are disengaged, and were always disengaged when attempting to focus.

  • All attempts have been stopped at this point

Reason for posting
I do not have access to a local SCT service technician. Before attempting anything, I wanted to understand what could have gone wrong? Once it is day time tomorrow, I will disassemble the ZWO EAF to see if the EAF is working correctly. Assuming it is, the next thing to fix would be the focus mechanism of the C8 Edge - which makes me nervous!

I’ve stopped all further mechanical attempts and want to proceed cautiously and correctly.

Thanks in advance — I value the depth of experience in this community.

Tony Gondola avatar
Tony Gondola avatar

You stated that the manual focuser won’t move in any direction, is that with the EAF detached because if that’s the case, the problem is on the SCT side, not the EAF side. Does the EAF function when not coupled to the SCT focuser?

Insightful
akshay87kumar avatar
akshay87kumar avatar

Tony Gondola · Jan 11, 2026, 07:17 PM

You stated that the manual focuser won’t move in any direction, is that with the EAF detached because if that’s the case, the problem is on the SCT side, not the EAF side. Does the EAF function when not coupled to the SCT focuser?

At this time, I have not disassembled the EAF from the focus mechanism. I will attempt it tomorrow to see if the problem is in EAF or the SCT side.

I do see that the EAF does attempt to twist both side visibly, but stops within half a second - as if it has hit some hard limit.

PS: I just edited my post to say "The EAF does not move in any direction” to avoid any confusion.