Having thought on this for a while and read through the thread again I am inclined to think that you can sort this collimation as Greg has suggested. Some time ago I came across a collimation PDf for an RCOS. A chap did exactly what Greg did and we all will at some point to clean the mirror. The adjustment screws are there on the back and it would be unreasonable not to expect the mirror would need cleaning one day.
My suggestion is this:
Consider buying a tak collimation scope or borrowing one. A chap I know here in SA might loan me one when I need to do mine, however I think I need one myself; there might be someone in your neck of the woods that has one too. It's all part of owning an RC. Take your time and pull the scope apart again. This time just inspect the entire mirror bottom. Look for registration marks, there is likely to be some and take a bit of look at the secondary but don't take it out of the tube. Just look for the same marks as Greg suggested. You should also take a look around for the other mystery shim. It might still be there or make sure you seated everything correctly on the first reassemble. You might have misaligned something and hence the reason for the wobble. I am inclined to think that this is the likely cause of the wobble, but I am not there. Once you have it altogether again use a Cheshire and look for alignment. I have looked through the back of my OTA with this and noted it was perfectly aligned and this would be a good tool to have too. If you have not touched the bottom screws don't unless you really have no other option but to move them. These screws should be considered as being your base line. Rotate the mirror until your secondary is centered perfectly if you cannot find any alignment marks. If there is alignment marks use the shims to center the secondary. This is going to take some time and you need to work on a kitchen table or somewhere comfortable. Once you have it all centered then prepare for a star collimation on a clear night.
It might not suit everyone but try to keep this in mind. Collimation is often required for folded optics. It is a skill that anyone can learn and when you get this sorted you will have a sense of accomplishment.
For people who feel it is necessary to make the thread about blame, please bear in mind that any folded telescope with optics exposed to the open will require the mirror being removed at least a few times in its life time. All RCOS telescopes have front and rear collimation screws as does the GSO from what I can gather. If the factory got it into collimation before then so can the average amateur. This is a hobby where you need to maintain equipment and adjust it if necessary. It is also a hobby that requires patience most of the time. Something we can all learn more of most of the time.
Peter this is achievable and you can do it. I would ask you post images of the entire back of the OTA disassembled. It could help us find the marks and help you. I would also urge you to contact a large astro society. ASSA holds collimation clinics and has lots of guys who know how to put equipment back together again, we even have a few opticians; maybe your society does too. We did this for years before commercial telescopes were available, we all made telescopes and pulled them apart and put them back together. If you lived near me I would come and take a look myself. I am not afraid to pull apart equipment and put it back together.
Post those images thanks.
