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Help interpret my unguided log

 

I do believe this is my first post!
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The attached unguided guidelog is from my CG-11 with several upgrades including brass worm gear on RA, new OPW blocks both axis, Gemini-II w/HT motors, somewhat recent new factory RA and DEC bearings, recent clean & lube with factory grease, I hope still cleaned/dry clutch pads, clutches minimally tight, 200mmFL guidescope. About 45 minutes of unguided time under below average seeing. The PE is rather high and looks to me jaggy, (and I wonder if that's indicative of mechanical, seeing or what.)
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On a good night I see about 0.75-1.0" rms in PHD2 and am currently imaging at 1.13" and 0.75", so I'd like to see if there's anything I can do to improve performance before I buy PEMpro and create a PEC curve.
?
Yesterday I removed and checked gearboxes/motors, also re-tightened oldham coupler set screws. Adjusted worm mesh but with the OPW this was just by feel - I simply push the worm into the wheel lightly and tighten everything down and if there is no stall I figure it's good - any advice appreciated!?
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Tonights experiment: if the clouds cooperate, playing with the RA worm mesh after sundown and mount cooldown as previously I'm adjusting at room temp which I know is not smart.?
--
Thanks,
Topher

PHD2_GuideLog_PE_2025-03-13_211848.txt
PHD2_GuideLog_PE_2025-03-13_211848.txt

 

Screenshots from the 3/13 log using Auto Filter:
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--
Thanks,
Topher
 

Log and screenshots from the following night without adjustments to the entire rig:
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--
Thanks,
Christopher

PHD2_GuideLog_PE_2025-03-14_140654.txt
PHD2_GuideLog_PE_2025-03-14_140654.txt

 

Frequency tab 3/13:
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Frequency tab 3/14:
--
Thanks,
Christopher
 

Hi Topher,
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A few things I see from your PHD2 log:
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1. There's a significant drift in RA. May be a large mirror flop, focuser sag, or just polar misalignment. It seems to reverse direction towards the end, which may mean it's more than just polar alignment error. Any thoughts as to what happened around 21:41 mark in RA when the drift changed direction?
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2. Even without the reversal at 21:41, the drift is significant, something like 150 arcseconds in 40 minutes, or nearly 4 arcsecs/minute. That's a large drift that will cause the autoguider to work hard to try to correct for it.
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3. With the drift removed, your data appears to show periodic error of about 14 arcsecs peak-to-peak, most of it at 1x the worm frequency @ 13 arcsecs and around 3 arcsecs at 2x the worm frequency. These should be easy to remove with PEC, once you fix the drift.
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Before you try programming PEC, I'd definitely recommend that you figure out what's causing such a large drift and fix it. If you don't know the reason for the drift reversal in your data, I'd investigate that, as well.
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Regards,
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? ?-Paul
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On Fri, Mar 14, 2025 at 03:30 PM, Topher wrote:

I do believe this is my first post!
?
The attached unguided guidelog is from my CG-11 with several upgrades including brass worm gear on RA, new OPW blocks both axis, Gemini-II w/HT motors, somewhat recent new factory RA and DEC bearings, recent clean & lube with factory grease, I hope still cleaned/dry clutch pads, clutches minimally tight, 200mmFL guidescope. About 45 minutes of unguided time under below average seeing. The PE is rather high and looks to me jaggy, (and I wonder if that's indicative of mechanical, seeing or what.)
?
On a good night I see about 0.75-1.0" rms in PHD2 and am currently imaging at 1.13" and 0.75", so I'd like to see if there's anything I can do to improve performance before I buy PEMpro and create a PEC curve.
?
Yesterday I removed and checked gearboxes/motors, also re-tightened oldham coupler set screws. Adjusted worm mesh but with the OPW this was just by feel - I simply push the worm into the wheel lightly and tighten everything down and if there is no stall I figure it's good - any advice appreciated!?
?
Tonights experiment: if the clouds cooperate, playing with the RA worm mesh after sundown and mount cooldown as previously I'm adjusting at room temp which I know is not smart.?
--
Thanks,
Topher
 

Hi Paul,
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Thanks for your thoughts and observations!!!
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No idea what could cause or did cause the RA drift to reverse on 3/14.
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The RA drift on 3/13 was about 200a/s in 40' with a PA error of 9.1. On 3/14 Drift was 140a/c in 40' with a PA error of 0.1. Better PA reduced the drift.
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I'm currently researching RA drift discussions on CN and so far have read thoughts on the cause being atmospheric refraction and the effect of tracking rate, (Sidereal vs King) on drift. Nothing yet on reversal. Still digging...
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And still trying to imagine how drift reverses. I've checked the guide scope/camera and I can't find anything not snugged down.
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--
Thanks,
Topher

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