Originally Posted by Arthur
But someone wrote it on the internet?!
You might have caught me out there - I think I've probably (definitely) written that somewhere on the tinterweb.
It can get you reasonably close but it depends on the scope. In the absence of using a better method, it's better than nothing. The mirror method is much better and the v block method is better still (although slow and a pita to do).
Go with the mirror method and see how you get on, although if you don't have adjustable mounts it's going to end up being fairly pointless at the end anyway, unless you're really lucky.