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The blocks evidently have changed.
This must be due to the change over to the spring-loaded worm.
I ordered a set of extra blocks when I did the Belleville washer modification, in case I needed them because of a screw up.
You can see in the picture, the blocks I ordered are completely anodized and the index peg on the right is not milled down.
The blocks that came with my mount, new in May, are milled down on one side. I assume this is to seat them tighter against the block holder.
The block on the right that pivots up and down away from the worm has the index peg milled down.
I assume this is because it needs more clearance room for pivoting as the worm rides up and down on the worm because of spring loading.

David,

I drilled and made my pivot hole larger. Most folks with new mount probably will not want to do that.?

Peter

Typically when using PEMPro, we use a hour or less of data to create a PEC curve which is then uploaded to the Gemini unit. Therefore we largely measure the behavior of the worm, and possibly some of the profile found on that section of ring gear. It would be nice to have data over the entire circumference of the ring gear, but that would take 24 hours of data, and some method of rotating through various sections of the ring. But how to maintain using the preferred best mating parts and only those parts is something I'm not sure the average user could do in practice. Since you can't see inside during operations, this may be difficult. But regardless of the random ring position which may be at CWD at a Cold Start, the PEC curve plays back with the same worm oscillations being repeated, and PE should be mostly negated for better guiding. Without PEMPro I can readily see the sawtooth pattern in PHD2 during guiding. I think we would all like to see better guiding performance without using a correction curve if possible

John,
I understand this. The problem is that Gemini has no way of knowing the physical position of the worm. My understanding is it either assumes the drive train is in the same position that is was or that it's where it was at CWD,? To have these positions be consistent the RA clutch must not be released or slipped. because it changes the drive train's orientation when the axis is at CWD..?

The only way stored PEC works is if the drive component positions remain known to the software. Without indexing, this can only happen if nothing is moved and the system is never cold started which resets the CWD position.?

On Mon, Aug 9, 2021 at 07:37 AM, Michael Ben-Yehuda wrote:

The only way stored PEC works is if the drive component positions remain known to the software. Without indexing, this can only happen if nothing is moved and the system is never cold started which resets the CWD position.?

No, clutches can be loosened and the mount moved manually without losing PEC index. Cold starting is also not going to affect it or changing CWD position.

The important thing is not to rotate the worm manually, without using Gemini motors. As long as the worm remains in the same position PEC playback will be sync'ed correctly to the worm.

Regards,

? ? ?-Paul?

The PEC curve obtained with PEMPro is something I can use for many months, despite numerous Cold Starts and clutch releases. If I make a mechanical adjustment to the mount, then the curve no longer applies and must be redone. Also over long periods of run time, the worm (and ring to some degree) will wear a tiny bit and the tracking can change accordingly. Despite my best efforts, I was not able to tune the mount to guide well without a PEC curve, despite the Bellville washer upgrades. I did decrease the RA play to lose most of that wiggle which can be found while rocking the end of the counterweight bar, but the sine wave worm oscillations were still present. But with PEC running and PHD2 variables adjusted, I am satisfied with guiding behavior, getting as low as 0.4 RMS error with excellent seeing, as I stated in another post. But 0.5 to 0.7 is common on the average night.