Bob's knobs are the go for sure. I don't know if the Celestron is anything like the meade but you can only adjust the secondary using allen keys. This is not recommended in the dark and the first time I tried I must have slipped onto the corrector a dozen times before I gave it up as a bad joke (ordered Bob's knobs that same night). I also had the secondary moving as I slewed around when I first bought the scope (not good for collimation!!!). After much reading on several forums the solution seemed to be locking one of the collimation screws down fully and using the other two to adjust. This has worked well and the scope holds collimation and focus well now. I wish mass produced scopes were perfect out of the box but half the fun of astronomy for me is tinkering and I wouldn't have it any other way
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