It is said that as one gets older one’s sensitivity to the extremes of
the visual spectrum gets less so more elderly observers may not find the
resulting false colour a problem. One reason being that the yellowing
of the eye’s lens tends to filter out the blue part of the spectrum. I
suspect that this is true and was somewhat amazed recently when I turned
my 80mm, f/5, achromat onto the Moon and could not really see any false
colour near the limb.
This may well be true. After cataract surgery I am very sensitive to blue fringe now where before I was not. Even in well corrected scopes if the eyepiece has any blue fringe I'll find it.
