Collimation Question!

[bonefish]

I have a collimation tool and knowhow to complete the process, but looking round the subject it seems the the primary mirror should have a centre mark on it i have noticed that depending where you look the centre can seem to be different, due to the off set angle you look at the mirror.

So how easy is it to remove the mirror to mark it, what would be best to centre mark the mirror to achieve true collimation.

My scope is a Skywatcher 130m.

Sounds simple but don't wish to really muck this up!

[sixela]

So how easy is it to remove the mirror to mark it,

Very. Remove cell from back of tube (make note of location of tube seam vs. the cell). Remove all the screws from the mirror clips. Remove mirror clips. Remove mirror from cell (also remove any backing that is behind the mirror while you're at it. It only prevents the mirror from cooling properly).

what would be best to centre mark the mirror to achieve true collimation.

Best? Large triangular centre spot plus template from CATSEYE Collimation Main Page Frameset File.

But some tracing paper plus a compass also works well to make a template, and binder reinforcement rings are quite good centre spots.