Hi Don,

You are confusing where the pole points in the heavens with where the center of rotation is on the earths surface. It's earth vs heavens.

The change in the center of rotation on earth (Chandler's Wobble) is minimal. One study suggests that in recent years there has been a very small drift in the center of the wobble. Extrapolating the findings, it would amount to only 11 arc-seconds over 4500 years.

While it is true that the point of sighting of true north in the heavens will change over time due to precession and the cycle of obliquity, an accurate sighting will always result in the same line on the ground.

As I have said before, however, if a method such as the vertical alignment of two stars very near the north point is used, that will result in different lines on the ground because the method is relying on a fixed point in the heavens rather than the moving locaton of the true north point.




C. Wayne Taylor
Richmond, Virginia USA