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Why don't you have a look at some ATM site and do it yourself?
It is quite easy thing to do (to determine your mirror is bad I mean) by using a point light source and edge (Fucault test, easy and widely used).
And of course, visual test on bright star (with good eyepiece) or difficult double should be enough to satisfy your first levels of curiosity.....
These tests, performed by others are not cheap, to do them may cost you more than new mirror (from GSO)
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