…continuedA Pupil Primer At the other end of the scale, there is
such a thing as too small an exit pupil. The basic limit is
imposed by the diffraction inherent in any telescope's aperture.
Use a magnification of more than 50x per inch of aperture, even
in perfect atmospheric seeing, and you're just magnifying
diffraction fuzz. This means the minimum useful pupil size for
any telescope is 0.5 mm. But even with a 1-mm pupil you're
likely to notice some bothersome effects. You may see your
retina's blood vessels superimposed on Jupiter, along with
"floaters" microscopic specks and strings of junk in your
eyeball fluid. Floaters tend to increase with age. Other fine
irregularities may be visible too. Normally the neural network
behind your retina does a remarkable job of image-processing all
these things out of view. However, it tends to get thrown for a
loop when the image is formed by narrow light cones from a tiny
pupil. This is only logical. The eye never uses a 1-mm pupil in
nature, so our visual processing