Primary mirror center marking

[Markus531]

I know I read a topic in here about center marking a primary mirror and I can't find it so I am gonna start a new thread. The thread I read mentioned about tracing the primary onto a piece of paper and cutting the tracing out. Then fold the paper into quarters and cut the corner where the two folds meet and that could be used as a template to find the center of the mirror. My question is: is there any margin of error? If you are off by a tiny bit will it effect the image drastically.

[nicnac]

Cleaning the Telescope Mirrors

here you go, this site should help

edit -: second half of page

[SteveA]

In relation to collimating the scope, obviously you want to be as acurate as possible with the marking of the mirror.

Bear in mind that with fast scopes (F/4 & F/5) the actual "sweet spot" you need to hit to achieve perfect colimation is about 1mm!...not much margin for error. With slower scopes there is more margin for error.

Remember though that the secondary mirror effectively blanks out an area of the primary mirror..and that region is never exposed to light..any mark on the primary in this area will never effect an image.