On Sun, Aug 4, 2024 at 06:18 PM, macdonjh wrote:
what can cause the worm phase to change between different nights (mine shifted by ~24s)?? Is there any way to "bring it back" (such as simply reloading the PEC curve I generated on July 20), or do I need to bite the bullet and make a new PEC run and load a new curve?
There is no worm index position sensor in Gemini -- there's only motor encoders that are used to report worm PEC index. Gemini remembers and restores the PEC index position from the previous session, automatically. The common causes for losing the PEC index:
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1. Rotating the motor while the worm is slipping or is completely disconnected from the mount -- Oldham coupler may be loose requiring the set screw to be tightened
2. 3v internal backup battery is wearing out, and can't keep and restore settings between sessions - check and replace if needed
3. Bad servo cable connection causing some encoder pulses to be missed - check that the cables are making good contact and the cable itself isn't broken or making intermittent connection
4. Loose encoder disk on the inside of the RA motor?
5. Sudden power loss or other kind of power spike or interruption that may have caused settings to be corrupted during one of the sessions
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In most cases, it's better to redo the PEC curve if the phase doesn't match the worm, rather than to try to readjust it.
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Regards,
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? -Paul
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Paul Kanevsky