Collimation question

Hi.
I have a C5+ which I recently tried to collimate.
Its rather decently collimated but at 250x high magnification, on one side of defocus, it isn't totally centered. Just one side.
I spent some amount of time trying to correct it, but I
never managed to get it fully centered on both sides of
focus. I'm not sure whats going on here.
Can anyone help?
Thanks.
Axel Dunstan

Could be a slight amount of mirror shift.

Axel,

I just went thru the same exercise with my NexStar 5, same tube. The diagonal was badly out of collimation. I switched to my good mirror diagonal and viola! problem solved. I discovered how bad the prism diagonal was off by installing it in my 80mm refractor and viewing it from the objective end.

There was a recent thread regarding diagonals and how poorly some are assembled. I have an identical prism diagonal which is perfect. (You know maybe I've got too much stuff....nah)

Good Luck!

Pete