http://legault.club.fr/collim.html
the images at the top are an inidcation. you notice it most whilst imaging at large magnification.
with my 5x powermate and my toucam acting as a 6mm eyepiece, i get 1044x, which you would never bother trying to look through. you are hoping to have your collimation spot on so that at this magnification, you can extract the most detail out of your movie you capture.
also, i find focussing better when the collimcation is good. you start with a defocussed image which looks like a CD rom and then you start to slowly focus it. you want to retain that circular shape all the way down to the tight focussed point for a star. if it starts get out of whack and your star grows hair, then the collimation is out