|
Break it down into two distinct stages.
First: The mirror, or lens for that matter concentrates the light into an image at the focal plane. Every available bit of aperture is used to form that image. That is a constant.
Second: An eyepiece is used to magnify the image at the focal plane. Different eyepieces will use different amounts of the image at the focal plane.
The resultant effect is that you get an image at whatever magnification and whatever FoV containing all of the light that the telescope collected for the object that you are observing, but not necessarily all the light that the mirror collected (ignoring the issue of exit pupil).
I think I'm going to have to lie down...
|