But, remember that a telescope can't make an object appear any brighter than as seen with the naked eye. Telescopes only magnify, and given that magnification the surface brightness of an object will either appear to be the same as seen with the naked eye (nearly, ignoring any transmission loss in the optics) or dimmer (but never "brighter," regardless of aperture).
Furthermore, the perceived brightness of an object is limited by the size of your eye's dark-adapted pupil and all a telescope can do is fill that pupil by some amount as determined by the size of the exit pupil from the optic system. So, while aperture does play a role in determining the size of the exit pupil (as a function of magnification) that doesn't allow a generalization to the effect that a larger aperture will produce a "brighter" image (under all situations). It really comes down to the size of the exit pupil (determined by aperture and magnification), your eye's dark adaption, and the apparent field of view of the eyepiece (the latter a consideration if the object/moon does or does not fill the entire field of view).
Having said that, it's generally true that given any particular magnification and eyepiece a larger aperture will produce a "brighter" looking image. But, if you change magnification or apparent field of view with a change of eyepiece or have an exit pupil that exceeds the size of your eye'e pupil then the determination becomes more complicated. In fact, once the size of the exit pupil from the eyepiece equals the dark-adapted size of your eye's own pupil the surface brightness of an object won't change with increased aperture (since the light from that increased aperture won't be able to enter your eye).
Also, for completeness I should add that all of the above applies specifically to the viewing of extended objects (like the moon), since point-source stars do appear brightened with increased aperture.
I have a question about this line of thought. Surely a telescope concentrates light. Obviously it cannot change the inherent brightness associated with any object, but it does concentrate the brightness of that object onto our retina. That is why, although I am aware of the sun's extreme brightness and would not ever look at it directly with my unaided eye, I certainly would absolutely never look at it unfiltered in a telescope because it could literally burn a hole through my retina. So, something tells me that I have just not understood you properly as you seem to me to be a very experienced and knowledgeable person even though I just don't think I've grasped your real teaching here. I have always viewed a telescope as a concentrator of light. Where have I gone wrong with this thinking... I never was very good at physics and have to admit that my common sense is frequently misguided. One last anecdote.... I once looked at the moon in a 25 inch F5 Obsession telescope and it was so bright compared to looking at the moon with my naked eye alone that I literally saw stars and was dazed... but I assume you might say that had something to do with my exit pupil diameter or something like that given your line of thought. Anyway.... I'm open to more knowledge Rick