Matt is spot on as usual...ummm, with all your 'supplied accessories' in use, you are definitely overpowering the t'scope. Even in good conditions I & (most I would say), never go anywhere near their max theoretical mag. eg; 10" dob = 500 x = no way Jose.
I normally view at about 120/180 x .....with good seeing conditions can go to 250/300 x, maybe a tad more...
L.