Periodic Errror

[CanisMajorTom]

Why is it that when a mount comes with Periodic error correction, and a periodic error cycle has been prgrammed in and activated, that the mount still has slight variations in the worm?

I would have thought that once you had programmed one cycle with the worm gear that the variations should be gone. But this is not the case on any mount. After teaching your mount it's periodic error, more teaching is required. Where does this other slack come from?

[Radar]

P.E.C doesn't correct every imperfection in the worm. It just makes the imperfections smaller. Which is why on mounts like my G-11, you need to do many training runs and then average them out. But even then, you still get RA drift.

[Red Giant]

I wonder if it is possible to train a worm to the point where there is no RA drift? I imagine that this cannot really be done. :pipethinker:

[CanisMajorTom]

I doubt it. Ambient temperatures would affect the worm gears ever slow slightly (if we are talking about metal worms) and because of this tiny amount of expansion / contraction, you would get periodic error. Other materials may not suffer from this though.