I have a ZWO EAF that's connected by a USB cable to an ASI2600MM Pro which is powered using the 12v 5a power supply sold on the ZWO website.

Last night at the start of my imaging session, I used NINA to control the EAF to establish focus. When focus was reached, the focuser shaft was nearly fully contracted. I started imaging and left the EAF connected. There were no instructions set up in NINA to attempt to re-focus at any point, and the NINA logs confirm it did not try to re-focus during the imaging session.

When I checked on my telescope in the morning, the EAF was beeping and the focus shaft was fully extended. By looking through my image files, I can see at about 7 hours into my session the EAF decided to randomly fully extend my focusing shaft.

Why did this happen?

How can I prevent it from happening again?

    The last image from my session that was in focus was taken at 4:03 AM. The first image out of focus was taken at 4:05 AM. Here is an excerpt from the log file when the problem happened (this shows the imaging software did not issue any commands to the focuser):

    2024-03-25T04:02:07.3127|INFO|SequenceItem.cs|Run|224|Finishing Category: , Item: Dither
2024-03-25T04:02:07.3167|INFO|SequenceItem.cs|Run|224|Finishing Category: , Container: NINA.Sequencer.Container.SequentialContainer, Strategy: SequentialStrategy, Items[FINISHED]: 1
2024-03-25T04:02:07.3177|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:02:07.3187|INFO|SequenceItem.cs|Run|206|Starting Category: Filter Wheel, Item: SwitchFilter, Filter: L
2024-03-25T04:02:07.3217|INFO|FilterWheelVM.cs|ChangeFilter|104|Moving to Filter L at Position 3
2024-03-25T04:02:11.1138|INFO|SequenceItem.cs|Run|224|Finishing Category: Filter Wheel, Item: SwitchFilter, Filter: L
2024-03-25T04:02:11.1138|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:02:11.1138|INFO|SequenceItem.cs|Run|206|Starting Category: Camera, Item: TakeExposure, ExposureTime 60, Gain 100, Offset 30, ImageType LIGHT, Binning 1x1
2024-03-25T04:02:11.1201|INFO|CameraVM.cs|Capture|732|Starting Exposure - Exposure Time: 60s; Filter: ; Gain: 100; Offset 30; Binning: 1x1;
2024-03-25T04:03:12.3003|INFO|SequenceItem.cs|Run|224|Finishing Category: Camera, Item: TakeExposure, ExposureTime 60, Gain 100, Offset 30, ImageType LIGHT, Binning 1x1
2024-03-25T04:03:12.3003|INFO|LoopCondition.cs|Check|75|LoopCondition finished. Iterations: 1 / 1
2024-03-25T04:03:12.3003|INFO|SequenceItem.cs|Run|224|Finishing Category: , Container: NINA.ViewModel.Sequencer.SimpleSequence.SimpleExposure, Strategy: SequentialStrategy, Items[FINISHED]: 2, Conditions: Condition: LoopCondition, Iterations: 1/1, , Triggers: Trigger: DitherAfterExposures, After Exposures: 3
2024-03-25T04:03:12.3013|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:03:12.3013|INFO|SequenceItem.cs|Run|206|Starting Category: , Container: NINA.ViewModel.Sequencer.SimpleSequence.SimpleExposure, Strategy: SequentialStrategy, Items[CREATED]: 2, Conditions: Condition: LoopCondition, Iterations: 0/1, , Triggers: Trigger: DitherAfterExposures, After Exposures: 3
2024-03-25T04:03:12.3013|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:03:12.3013|INFO|SequenceItem.cs|Run|206|Starting Category: Filter Wheel, Item: SwitchFilter, Filter: R
2024-03-25T04:03:12.3043|INFO|FilterWheelVM.cs|ChangeFilter|104|Moving to Filter R at Position 4
2024-03-25T04:03:13.0319|INFO|StarDetection.cs|Detect|246|Average HFR: 5.21266526743259, HFR σ: 0.603974672546185, Detected Stars 69, Sensitivity Normal, ResizeFactor: 0.25
2024-03-25T04:03:13.2168|INFO|BaseImageData.cs|FinalizeSave|162|Finalize image and moving it to C:\Users\scope\Documents\N.I.N.A\2024-03-24\LIGHT\2024-03-25_04-02-11_L_-4.90_60.00s_0048.fits
2024-03-25T04:03:14.0353|INFO|SequenceItem.cs|Run|224|Finishing Category: Filter Wheel, Item: SwitchFilter, Filter: R
2024-03-25T04:03:14.0363|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:03:14.0363|INFO|SequenceItem.cs|Run|206|Starting Category: Camera, Item: TakeExposure, ExposureTime 120, Gain 100, Offset 30, ImageType LIGHT, Binning 1x1
2024-03-25T04:03:14.0423|INFO|CameraVM.cs|Capture|732|Starting Exposure - Exposure Time: 120s; Filter: ; Gain: 100; Offset 30; Binning: 1x1;
2024-03-25T04:05:15.1737|INFO|SequenceItem.cs|Run|224|Finishing Category: Camera, Item: TakeExposure, ExposureTime 120, Gain 100, Offset 30, ImageType LIGHT, Binning 1x1
2024-03-25T04:05:15.1737|INFO|LoopCondition.cs|Check|75|LoopCondition finished. Iterations: 1 / 1
2024-03-25T04:05:15.1737|INFO|SequenceItem.cs|Run|224|Finishing Category: , Container: NINA.ViewModel.Sequencer.SimpleSequence.SimpleExposure, Strategy: SequentialStrategy, Items[FINISHED]: 2, Conditions: Condition: LoopCondition, Iterations: 1/1, , Triggers: Trigger: DitherAfterExposures, After Exposures: 3
2024-03-25T04:05:15.1737|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:05:15.1737|INFO|SequenceItem.cs|Run|206|Starting Category: , Container: NINA.ViewModel.Sequencer.SimpleSequence.SimpleExposure, Strategy: SequentialStrategy, Items[CREATED]: 2, Conditions: Condition: LoopCondition, Iterations: 0/1, , Triggers: Trigger: DitherAfterExposures, After Exposures: 3
2024-03-25T04:05:15.1747|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:05:15.1747|INFO|SequenceItem.cs|Run|206|Starting Category: Filter Wheel, Item: SwitchFilter, Filter: G
2024-03-25T04:05:15.1767|INFO|FilterWheelVM.cs|ChangeFilter|104|Moving to Filter G at Position 5
2024-03-25T04:05:15.8733|INFO|StarDetection.cs|Detect|246|Average HFR: 12.0996953510046, HFR σ: 3.97424855205711, Detected Stars 2, Sensitivity Normal, ResizeFactor: 0.25
2024-03-25T04:05:16.0562|INFO|BaseImageData.cs|FinalizeSave|162|Finalize image and moving it to C:\Users\scope\Documents\N.I.N.A\2024-03-24\LIGHT\2024-03-25_04-03-14_R_-4.40_120.00s_0048.fits
2024-03-25T04:05:17.1300|INFO|SequenceItem.cs|Run|224|Finishing Category: Filter Wheel, Item: SwitchFilter, Filter: G
2024-03-25T04:05:17.1310|INFO|MeridianFlipTrigger.cs|ShouldTrigger|221|Meridian Flip - Flip for the current target already happened at 3/25/2024 2:15:40 AM. Skip flip evaluation
2024-03-25T04:05:17.1310|INFO|SequenceItem.cs|Run|206|Starting Category: Camera, Item: TakeExposure, ExposureTime 120, Gain 100, Offset 30, ImageType LIGHT, Binning 1x1
2024-03-25T04:05:17.1390|INFO|CameraVM.cs|Capture|732|Starting Exposure - Exposure Time: 120s; Filter: ; Gain: 100; Offset 30; Binning: 1x1;
2024-03-25T04:07:18.3431|INFO|SequenceItem.cs|Run|224|Finishing Category: Camera, Item: TakeExposure, ExposureTime 120, Gain 100, Offset 30, ImageType LIGHT, Binning 1x1
      5 days later

      Matt0011 Thanks for your log, the filter was changed during that time, do these filters have the same focus position?

          Matt0011 Check if all set screws on the coupler are tightened. i suspect the focuser may moved.

              Tech@ZWO Yes, they're all tight. There was no movement. The problem is the EAF started running on its own and didn't stop for at least 2 hours (it was continuously beeping because it kept trying to run even though it was at its limit) until I came out and disconnected it.

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