(1) Dust, haze, crud between the elements is one reason
for factory service. If you are careful in storing
and using the eyepieces, it will probably be a very long
time before this is an issue.
(2) Cement between elements becomes cloudy or separates
from glass. I see this alot in certain brands of
eyepieces from the 60s and 70s.
(3) Lens coatings flake off. Usually if they are
properly coated this does not happen. But again I have
seen a fair number of very old eyepieces where the
coatings are partially gone, even on the internal surfaces.
I suspect they were not coated properly in the first
place. I can think of two models of old eyepieces where
everyone I have seen has the coating coming off one
particular surface inside.
for factory service. If you are careful in storing
and using the eyepieces, it will probably be a very long
time before this is an issue.
(2) Cement between elements becomes cloudy or separates
from glass. I see this alot in certain brands of
eyepieces from the 60s and 70s.
(3) Lens coatings flake off. Usually if they are
properly coated this does not happen. But again I have
seen a fair number of very old eyepieces where the
coatings are partially gone, even on the internal surfaces.
I suspect they were not coated properly in the first
place. I can think of two models of old eyepieces where
everyone I have seen has the coating coming off one
particular surface inside.
