cleaning optics?

can some optical coatings be damaged by some cleaners?.

ive noticed that if you blow dry the lens with a air duster after using
a liquid cleaner it leaves no tide mark on a camera lens but some
liquid cleaners could damage coatings, ive got acetone but never
used it as i feel it could do some harm. what about alchohol (not the nice
tasting
veriety ). cotton buds and camera lens cleaning tissues are the other things
that come to mind
as being useful.

of course the best thing is to not let the lens get dirty in the first
place.

any experiences/advice etc much appreciated

"Simon" wrote in message
news
can some optical coatings be damaged by some cleaners?.

ive noticed that if you blow dry the lens with a air duster after using
a liquid cleaner it leaves no tide mark on a camera lens but some
liquid cleaners could damage coatings, ive got acetone but never
used it as i feel it could do some harm. what about alchohol (not the nice
tasting
veriety ). cotton buds and camera lens cleaning tissues are the other
things
that come to mind
as being useful.

of course the best thing is to not let the lens get dirty in the first
place.

any experiences/advice etc much appreciated



Students and the general public are real problems for eyepieces at
university observatories. But you have to teach them. I have often thought
of fingerprinting the lot at the start of Term and determining the guilty
parties that way.

Eyepieces, camera lenses: I use isopropyl alcohol (lab grade) and soft
surgical grade cotton from the chemist (not artificial cotton or buds on
sticks, except very sparingly for small optics). First wash your hands
thoroughly with detergent and running water. This gets most of the oils off
your skin and minimises transfer via the cotton. You may need to clean a
lens more than once to get completely rid of any greasy marks such as
fingerprints or sleeks from first cleanings. Be very very gentle, minimum
pressure. The first one should be just to wet the surface with no rubbing.
Take care not to get any significant amount of alcohol inside the eyepiece
or lens as it could harm the optical cement joining multi-element parts
(i.e., don't use a lot, just a bit). After one use, dispose of the cotton
and use a fresh piece. After three or four repeats, the surface should look
clean under a bright light.

The other advice is to clean things ASAP after any accidental dirtying.
Left in place, the acids in fingerprints can eat their way into a coating.

Acetone is also a powerful solvent but has the annoying properties of being
highly flammable and a knockout agent. It needs much greater care such as
adequate ventilation. Alcohol works fine. In an emergency, in the field, I
have used gin to clean a camera lens on a digital camera and it worked very
well.

Use the above methods and steer clear of so-called lens wipes. These
encourage using pressure.

The best advice for front surfaces of catadioptric telescopes is don't clean
them. At most blow the dust off. They can look horrendous by reflected
light but it takes a lot of dirt to cause significant problems. Keep scope
covered and dry when not in use.

www.ulo.ucl.ac.uk

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

thanks for that comprehensive reply Mike

Simon
"Mike Dworetsky" wrote in message
...
"Simon" wrote in message
news
can some optical coatings be damaged by some cleaners?.

ive noticed that if you blow dry the lens with a air duster after using
a liquid cleaner it leaves no tide mark on a camera lens but some
liquid cleaners could damage coatings, ive got acetone but never
used it as i feel it could do some harm. what about alchohol (not the
nice
tasting
veriety ). cotton buds and camera lens cleaning tissues are the other
things
that come to mind
as being useful.

of course the best thing is to not let the lens get dirty in the first
place.

any experiences/advice etc much appreciated



Students and the general public are real problems for eyepieces at
university observatories. But you have to teach them. I have often
thought
of fingerprinting the lot at the start of Term and determining the guilty
parties that way.

Eyepieces, camera lenses: I use isopropyl alcohol (lab grade) and soft
surgical grade cotton from the chemist (not artificial cotton or buds on
sticks, except very sparingly for small optics). First wash your hands
thoroughly with detergent and running water. This gets most of the oils
off
your skin and minimises transfer via the cotton. You may need to clean a
lens more than once to get completely rid of any greasy marks such as
fingerprints or sleeks from first cleanings. Be very very gentle, minimum
pressure. The first one should be just to wet the surface with no
rubbing.
Take care not to get any significant amount of alcohol inside the eyepiece
or lens as it could harm the optical cement joining multi-element parts
(i.e., don't use a lot, just a bit). After one use, dispose of the cotton
and use a fresh piece. After three or four repeats, the surface should
look
clean under a bright light.

The other advice is to clean things ASAP after any accidental dirtying.
Left in place, the acids in fingerprints can eat their way into a coating.

Acetone is also a powerful solvent but has the annoying properties of
being
highly flammable and a knockout agent. It needs much greater care such as
adequate ventilation. Alcohol works fine. In an emergency, in the field,
I
have used gin to clean a camera lens on a digital camera and it worked
very
well.

Use the above methods and steer clear of so-called lens wipes. These
encourage using pressure.

The best advice for front surfaces of catadioptric telescopes is don't
clean
them. At most blow the dust off. They can look horrendous by reflected
light but it takes a lot of dirt to cause significant problems. Keep
scope
covered and dry when not in use.

www.ulo.ucl.ac.uk

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

Good job you asked.
Yes, telescope optics are normally coated and will be damaged if you try to
clean them.

The best thing that can be used to clean a scope is distilled water - the
purer the better. Or better yet - don't touch the optics. The airduster
will clean off the loose dust and that will be good enough. The only time
that you should consider going near the optics with any kind of liquid is
when there is a grease mark (like a finger mark) on it. Then, I'd suggest
that you look up Doc Clay's cleaning solution in google.

Regards

Colin Dawson
www.cjdawson.com



"Simon" wrote in message
news
can some optical coatings be damaged by some cleaners?.

ive noticed that if you blow dry the lens with a air duster after using
a liquid cleaner it leaves no tide mark on a camera lens but some
liquid cleaners could damage coatings, ive got acetone but never
used it as i feel it could do some harm. what about alchohol (not the nice
tasting
veriety ). cotton buds and camera lens cleaning tissues are the other
things that come to mind
as being useful.

of course the best thing is to not let the lens get dirty in the first
place.

any experiences/advice etc much appreciated