RA spikes at worm gear period

[John Sayers]

https://openphdguiding.org/logs/dl/PHD2_logs_xJ8h.zip

Any ideas about what is causing this?

[Brian Valente]

John

A loose worm block causing lateral worm movement, or a bad PEC come to mind. 

what's the mount and the primary period length?

On Fri, Dec 26, 2025 at 8:39 PM John Sayers <johnsa...@gmail.com> wrote:

https://openphdguiding.org/logs/dl/PHD2_logs_xJ8h.zip

Any ideas about what is causing this?

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Brian 

Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

[John Sayers]

Brian

The period of the worm is 483.45. I have the PPEC set to Predictive Weight 62 and Reactive Weight 60. The mount is a Skywatcher EQ6R-Pro. The spikes will  appear between 50-60° Alt. then stop above 80° when the OTA is on the west side and facing NNE.

[John Sayers]

Brian,

After replying to your post I checked the mount and found the 2mm hex set screw on the bottom of the RA block to be very loose. I snugged it to match the top screw, may be the problem. I believed all along the problem to be mechaincal.

I will let you know if this correction works.

Thanks,

John

On Saturday, December 27, 2025 at 12:32:29 AM UTC-5 bval...@gmail.com wrote:

[Brian Valente]

John glad to hear you found it. A loose screw can certainly explain lateral worm movement

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[Brian Valente]

PS

>>>The period of the worm is 483.45. I have the PPEC set to Predictive Weight 62 and Reactive Weight 60.

if you know the worm period disable PPEC auto adjust period and set it to the known value. 

 

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