Will cone error cause erroneous Polar Alignment using EKOS's PA routine?

I don't think cone error is a problem for polar alignment.

I believe cone error means that the OTA is not aligned with the mount, which is similar to running polar alignment with a non-90º dec angle (in the north). Since the polar alignment really should work anywhere in the sky, I'd say that it should work with cone error.

Hy

The reason I question it is because I experience something many others here have - in that when I polar align by slewing East of the pole, and the go back and slew West of the pole the alignment is off again. I can nit make the two directions equal.

In the same trend I made my suggestion to polar align symmetrically. My approach is to reduce flexing/bending of the mount/pier, your question addresses the angle between the scope and the mount.

With some initial testing/measurements last night, I noticed the backlash on the worm and the worm gear of the RA axis is of greater impact than the polar alignment deviation.

And I think this first conclusion can be generalized: the backlash on the RA axis is probably going to have a bigger impact than the conical error.

Are there other forum members who have already done research on this?

I don’t think my pier is bending. It’s 12 inches wide reinforced concrete that is five feet deep in the ground. The mount is a CEM120 EC2 with a payload max over 100 pounds and I just have a single C11 on it. The dual encoders prevent backlash errors.

Perhaps primary mirror in the scope itself is shifting, or the image train somewhere.

Woooowwww fantastic !
Seems to be somewhere in the Spanish heartland ?

And your CEM isn't going to have that much backlash either.


I can only dream of that...

In the meantime I've found some of your pictures on the forum, they are really impressive !

And apparently your observatory is in New Mexico, which is even better than Spain.

Given you have a C11, perhaps mirror shift is the root cause of the difference you're seeing. Try the same procedure with a refactor and see if there is a difference.

jmh

Yes, mirror flop was the first thing jumping to my mind when reading this. Like Hy, I think PA should not be affected by cone error. Mirror flop would explain it. As well as play in the optical train. Is it all threaded connections?

With an EC mount you should be able to just track (unguided) through meridian and watch for a systematic shift of the image. How far can you track past meridian? iOptrons aren't particularly good at that

Yes, all threaded. I’ve never tried tracking past the meridian over 3 minutes. I could try but not sure how to tell my dome to follow. It has a mind of its own when it comes to flips. But I guess I could just turn off the sync and rotate it manually if needed.