I hope this will be helpful to some of you who use iOptron’s iPolar.
I found a way to greatly improve the accuracy of iPolar (I have a CEM70, but the following can probably be applied to other mounts). The idea is to measure the center coordinates multiple times (e.g. 10 times) with the mount in various orientations (this is important), average all the coordinates, and finally enter the average value for X and Y manually in the iPolar software settings. Additionally, for each measurement, after confirming position 1 and before moving to position 2, put your hand in front of the iPolar camera and rotate the RA axis manually, about 45°. As soon as you remove your hand, the iPolar software will confirm position 2. If you don’t put your hand in front of the camera, the iPolar software will confirm position 2 almost immediately, with a very small rotation angle, which likely reduces the accuracy. With this, and a properly executed polar alignment, I was able to take fairly long unguided exposures with minimal star trailing (only the periodic error, along the RA axis, shows up in unguided exposures, which obviously can be fixed with PEC to some extent, or with guiding) Also, the Go-To accuracy is incredible!
Hope this helps!
Note: I use iPolar software version 2.50 (latest version at the time of this writing)