[mikeyjames (Mick)]

Originally Posted by doppler

That may be what is known as cone error. Here's a video that will explain what it means and how to adjust your scope.
https://www.youtube.com/watch?v=WatdQlPp22Y

or a quick read http://www.cloudynights.com/page/art...rocedure-r2447

Thanks Rick, just watched the video and it seems to be exactly what I need.