42 August 2014 sky & telescope
Telescope Maintenancewith Windex, then slowly and gently wipe from the center
of the optic outward with a circular motion, continuously
using fresh cotton. I don’t need to apply pressure for the
cleaning solution to do its work, but I may need to go over
the glass a couple of times before it’s completely clean.
Finally, I fog the glass by breathing on it, and I use a freshcotton ball to wipe the surface one last time.
Sometimes you’ll see spots and blemishes that simply
won’t go away. Chances are these aren’t stains, but rather
places where the coating has been damaged by acid dew or
some other cause. There’s nothing you can do about these,
just recognize them for what they are and console yourself
with the knowledge that they don’t aff ect the view.Eyepieces and Filters
Eyepieces and fi lters should receive the same treatment
as objective lenses, except that they require more fre-
quent attention because they get handled a lot. Even if
you’re careful, it’s likely that the outermost lenses of your
eyepieces will eventually accumulate a coating of eyelash
oil. This means that you’ll need to use a cleaning sol-
vent once you’ve blown away or brushed off all the loose
dust. The only real diff erence with cleaning these small
surfaces is that you’ll use Q-Tip cotton swabs rather than
cotton balls. As above, Windex works well, but acetone is
an option if you’re certain there are no plastic or painted
parts in the eyepiece or fi lter. It’s also important to ensure
you don’t apply liquids directly to the glass — lightly
dampen the Q-Tip with the liquid, then gently and slowly
wipe the lens, using a circular motion.
Use as little of the cleaning solution as you can and
avoid wiping too quickly. If you don’t, little droplets of sol-
vent can remain on the glass, and when these evaporate
they often form small spots that require additional clean-
ing. As a fi nal step, fog the lens with your breath, then
go over the surface with a clean Q-Tip. If you have a lot of
oily build up on your eyepiece, you may have to repeat the
process several times before it’s completely removed.
Under no circumstances should you ever take an
eyepiece apart. If you have an objectionable amount of
dust on the interior lenses of an eyepiece, a trip back to
the factory is your best bet. Al Nagler tells me that one of
the main reasons an eyepiece is returned for servicing is
because its owner took it apart and couldn’t put it back
together properly.
Cleaning optics is just part of the package when you
become a telescope owner. Although the process can
seem intimidating at fi rst, eventually it will become
routine. And this is when you have to exercise the great-
est care. Don’t become complacent, and make sure you
take all the necessary precautions when cleaning your
optics. And don’t start cleaning them more frequently
than necessary because you’ve become comfortable with
the process. If you use the methods described here, and
only do so when you really have to, your telescopes and
eyepieces should last a lifetime. ✦Contributing editor Gary Seronik has been building and
cleaning scopes for more than three decades. He authors this
magazine’s Telescope Workshop column and can be con-
tacted through his website: http://www.garyseronik.com.Cleaning the small lenses in eyepieces is just like cleaning a tele-
scope objective lens, except that cotton swabs rather than cotton
balls are used.Telescopes and eyepieces will deliver a lifetime of fi rst-rate views
if cleaning is done carefully and only when necessary.