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OK, think of the starlight as a wave that hits the entire Earth. The light from that star fills the entire mirror. This is true for every star in the field of view. For every eyepiece.
And it would be true if your telescope were 100 meters across.
What the eyepiece does is determine how much of the parent focal plane of the telescope is examined.
But the entire mirror is used for every point on that focal plane (excepting the umbra of the secondary shadow).
[In fact, as little as seventy percent of your mirror is illuminating a spot at the edge of the field of view, but that is because the secondary mirror isn't large enough to retrieve the entire light cone at every angle, not because the primary isn't receiving the light.]
Stopping down the mirror will reduce the brightness of the image, but using a different eyepiece does not.
Larger eyepieces see a larger portion of the telescope's focal plane (hence, a larger field of view), but they cannot make the star images brighter and they do not use any more or less of the mirror's surface.
Hope that explanation makes sense.
Don
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