The Adaptor screws onto the visual back of your SCT and the laser fits into the adaptor. At left below you can see the laser as it would be when put into the adaptor. A laser collimator works by projecting a thin red beam of light onto the optical components of your Newtonian or Schmidt Cassegrain telescope. If it does not, then collimation procedures need to be followed. Each collimator comes with an Allen wrench for those who want to tweak or adjust their collimator.
All collimators come factory aligned.
A paper reinforcement ring is included to mark the center of your Newtonian primary mirror. In the SCT Collimators, a small round label is included that is stuck onto the face of the collimator to mark the point where the collimator beam returns. The laser is placed into your focuser. Your diagonal mirror will now have a red dot on it. It should be exactly centered on your mirror.