I removed the primary from my RCOS 12.5 inch once and cleaned it and refitted it and recollimated it. It wasn't that hard.
If you haven't touched the secondary then it consists of:
1. Aligning the primary and secondary index marks (mine had a paint mark on the side of the primary and secondary so you rotate the primary's mark to line up with the secondary's mark.
2. You can do something as simple as a plastic cap with a hole in the centre that fits in the visual back. Now line up the spider cross so that the secondary and primary form concentric circles.
3. I used a Tak collimation scope here to get this alignment very accurate.
4. Final tweak using a star (I didn't do much here as it was pretty close and small adjustments made a pretty large difference.).
Also following a thread on another RC site (A&M RCs) they flocked the secondary mirror light shroud to stop unwanted reflections from bright stars just outside the range of the image.
You can also download a free trial of CCD Inspector which has a live collimation tool to get it exact using a CCD camera.
As far as shims etc go I presume they were put there to ensure the primary was square to the tube. Perhaps the back of the mirror is not
even and so it needed shimming. So put it in and adjust the shims so it is stable and appears square perhaps a cheap laser collimator may be helpful there too.
I imagine the shims also help put the collimation adjustment into the correct range of the adjustment screws in the case where it is quite a ways off.
Perhaps this helps.
Collimation isn't really that difficult, you just need a set of instructions.
Try the above and see how you go.
There was also the link I posted to the RCOS collimation instructions. They were the ones I used. When you get up to the point where you need a Tak collimating scope perhaps you can subsitute a cheap laser collimator. It saved my bacon when collimating a fast F4 200mm Vixen that was difficult to collimate before I used the cheapie Antares laser collimator from Scope Stuff (
www.scopestuff.com).
You know there's no way around it for any RC or compound scope owner, learning how to collimate is a basic skill that you're going to have to confront learning at some point as the fact is compound scopes collimation will not always hold, especially if you travel with it. Admittedly adjusting it from parts is going to be the hardest.
Greg.
