|
That is not really enough to show what is going on. The position of the spider and secondary need not be centred (and won't be for a properly collimated 10" dob because of 2ndary offset).
Assuming your secondary is good enough, what you need to do is place something highly reflective on the back of the film canister and then illuminate it so that you can see its reflection through the the hole in the film canister in the focuser. Then adjust the primary tilt until reflection of the back of the film canister is centred on the centre spot of the primary.
PS. I've attached a more browser-friendly version of Shane's drawing.
|