I've attached a drawing of what I see in my scope (10" reflector/dob) when I look thru my home-made collimation tool, a 35mm film canister.
The reflection of the "centreing" mark on my primary is a bit off-centre. My question is: what needs to be adjusted - the secondary mirror's placement in its holder, the arms of the spider on the secondary, or the primary mirror?
I've looked at a number of collimation-related sites but havent yet found the answer to this one!
Help?
