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There was another question within a question... And the answer is below :-).
Magnification does not add to the surface brightness of the extended objects, quite the opposite.
So, watching Moon with 100x is actually 100 times safer than watching the moon with 10X, because the apparent surface at 100x is 100 times larger (square law) than at 10x, and the amount of light is the same (provided the whole Moon can fit in the 100x eyepiece field of view.
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