i've built/assembled 2 small refractors with pvc --- the second made me aware of collimation :-), 20yrs later i've bought a cheap 8"@f5, all the collimation tools are diy .... in process of making the test tools to start grinding on a 10' f/5ish, (got the marking turntable done to take 16" blank and acquired 1 rail from a scrap surface grinder to serve as my test bench)..... also working on SPC900 w/raw mod hoping to do SC for exposure and gain even though the raw mod gives good output.