Hi All,
I have a 10" GSO dob and I'm still struggling a bit to understand the whole collimation thing. I purchased a catseye cheshire with the center spotting template and today I removed the old center spot, put on the catseye triangle and attempted to collimate my scope. I have also ordered a Techron site tube to configure the secondary correctly but haven't received that yet. The procedure I followed was to use my laser collimator to tilt the secondary so the beam hit the center hole of the catseye spot then used the catseye cheshire to align per instructions by tilting the primary. What I ended up with was something like this:
http://www.zitafarm.com/astro/collimate.jpg
So, my question is, why is the cheshire reflection (gray ring) so far off center? I know my laser collimator is dodgy (although it is correctly collimated), it was so poorly machined that the centre spot moved 2 cm when tightening the focuser set-screw, in the end I wrapped it with tape to make the fit tight like the cheshire (which is a perfect fit). I'm assuming this all has something to do with secondary centering and that I'll be able to sort it with the sight-tube when I get it.. am I on the right track? Thanks! Bruce.