Newbie with Skywatcher 200p - Tube rings affecting collimation? in Discussions - Mounts Posted October 28, 2009 I had a problem when my scope was new in that I thought the spider had become loose - so I tightened the loose screw. I then saw that the screw was OBVIOUSLY a couple of turns loose again! The reason, it turned out, was that the tube is very thin and the spider arm threads were catching on the tube. The nuts on the spider were simply tightening onto the tube wall and were NOT tightening the spider. Once I realised this there have been no further troubles. (I hope the above makes sense!) - It may help you as well.