On 27 Dec 2004 11:06:09 -0800, "canopus56"
wrote:

Suiter's 1994 classic, _Star Testing Astronomical Telescopes_
(Willman-Bell), suggests the following test (on p. 240), which I have
not personally tried:

"Your eye also suffers from medium scale roughness. Take aluminum foil
and perforate it with a pin. Hold the foil about 8 to 15 cm in front
of your eye and look through the pinhole at a frosted incandescent
light bulb. Try to focus your eye on the lamp, not the pinhole, and
cover the other eye. If you have punch the right size hole in the
foil, you should see a mottled disk that roughly approximates the
out-of-focus patterns seen in this book. . . . . The appearance may be
cleared up slighty by placing a colored [telescope lens] filter between
the lamp and the pinhole.

I have a corneal opacity in my right eye that I can see when I look
through a pinhole at a moderately bright light. Because of the
opacity my right cornea is "lumpy". I can look at the Moon and see
several fainter, false moons clustered around the real one.

When you look at the sunlit face of the moon at extremely high power
some of what you see is actually the structure of your eye illuminated
by the highly collimated rays of light coming through the eyepiece.