Step by step
Do your first collimation in the daytime, when you can see what’s going on. Secure your Cheshire eyepiece collimating tool in the focuser with the open side facing the sky to let light in. Next, point the scope at the bright sky, but well away from the Sun.
Through the tool’s eyehole look for the centre ring on the primary mirror. Move the secondary mirror with the adjuster screws to bring this ring under the point where the shadow of the crosswires intersect. You may need a screwdriver or other tools for this.
Now align the primary mirror using its adjustment screws, until the peephole spot is centred in the main mirror’s centre ring. If you moved the primary a lot you may need to re-check the secondary alignment, but otherwise your scope’s collimated and good to go!
Secondary support vanes
Familiarise yourself with the view through the collimating tool’s eyehole. What you see may be confusing at first, so compare your view with the labelled image above for a mis-collimated scope. This will help you to identify the features that need to be repositioned.
When the first stage of collimation is done the view should look like the one above, with the centre ring on the primary mirror right under the middle of the cross-wire shadows. Tighten up the secondary mirror screws, being careful to maintain alignment.
Next time you perform any fine-tuning collimation it may be at night. In this case, shine a red torch into the side of the collimating tool to illuminate the middle of the cross-wires and show the dark collimating tool’s eyehole.