You may be having similar problems to what I had with my Meade 16", which is part of why I rebuilt it into a truss mount system. However, here's what I did to find the problems on mine... First, check the tube assy and make sure the focuser is square to the tube path. Frequently one side get tightened more than the other, the sono-tube indents a bit, and presto - you got a problem. Take the thing off. Measure carefully from end of tube to center of hole - and make a mark directly opposite on the tube where "straight accross" should be. Remount the focuser and align so that mark is visible thru a pin-hole (use collimating ep reversed in focuser). Now mount secondary, amd make sure its centered on that same center line. Both of these were badly off on mine - focuser tilted and secondary set too far into the tube. Had to build a new spider it was so bad! After that, standard collimation should fix you up. Good luck with it! Takes time...