mBuxx These are guided though and I'm not sure if this is what's correcting any PA issue.
Guiding is precisely what keeps an imperfect mount working.
Polar alignment is no more and no less that a process that tunes the RA axis of your mount to point directly at one of the celestial poles.
When the mount is not perfectly aligned, the track that a star makes will not have at a perfectly constant declination angle on the mount, and the star will not move at the rate the RA is tracking (called the sidereal rate).
If the aligment error is small, guiding will correct for it. I.e., the guide star will stay put. When the guide star moves a little, autoguiding will direct your mount to recenter that star.
However... there is one thing that autoguiding will not cure. And that effect is called field rotation. "Field" just means the field of view of your telescope, and "rotation means just that-- the entire field will appear to slowly rotate around a certain point. If you are autoguding, that point (center of field rotation) is the location of the guide star.
The guide star does not move in a long exposure, but all other stars appear to rotate around it.
The amount of roatation is related to how far the RA axis is away from the pole.
In short, yes, autoguiding (or manual guiding, for that matter, using an eyepiece) will mask some of the error from bad polar alignment. But it cannot get rid of field rotation.
For practical exposure times, an RA axis error of 1 arc minute is sufficient to make all the stars appear stationary, so there is no need to over do polar algnment.
Chen
