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#1 Glassthrower


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Posted 30 September 2005 - 10:53 PM


There have been countless debates about the correct methods for cleaning the optics
of your telescopes/binoculars. There have also been an endless chain of horror stories
about cleanings gone wrong and damaged lenses/mirrors. Bearing this in mind, the very
best way to keep your optics clean is to NEVER LET THEM GET DIRTY IN THE FIRST PLACE.

Don't ever ever ever touch your optics for any reason. A tiny speck of dust on a lens
is preferable to a scratch caused by a well-meaning but incorrect cleaning method. The dust
can always be removed in the proper manner, a scratch is permanent. So if in doubt, just
leave it alone and don't touch it.

If there is a speck of dust, a tiny grain of sand or dirt, or something similar on your
lens, then use a VERY SOFT, natural-hair brush to flick the offending particle up and
away from the lens. Using a gentle flick of the wrist, "kick" the dirt or dust outward
towards the rim of the lens. This should be combined with a simultaneous upward motion.
Using this technique will ensure you do not rub or drag the dirt particle across the glass,
forming a permanent scratch.

A stubborn grain of dirt may require additional motivation to vacate the lens surface.
Do NOT blow on the lens using your mouth or breathe on the lens. Your telescopes or
binoculars are not sunglasses, so don't even think about breathing on the lens to form
a vapor and wipe it off. This is forbidden! And even though it may seem like a good idea,
resist using cans of compressed air to blast dirt/dust from your lenses. Canned air uses
propellants which can (and usually do) escape from the nozzle and land on your lenses. The
propellants used are a variety of nasty substances that can and will damage the sensitive coatings
on your optics. So what is one to do? Use a squeeze bulb, atomizer, or specially-made "blower brush"
to gently direct a puff of air onto the offending dirt speck.

Beware of pre-moistened "lens cleaning cloths" that come packaged like disposable hand wipes. These
are sold on drug store shelves and in checkout lines for use primarily on eyeglasses. A check of
the package usually reveals a claim that the cloths are safe for use on coated optics, binoculars, camera
lenses, etc. Do not trust this claim with your optics. If the exact cleaning agent used is not
identified on the package then do NOT use it. Many of these cloths or wipes contain a cleaning solution
that is oily in nature and is extremely difficult to completely remove. Some may contain a solvent or
harsh chemical like ammonia. Again, don't use them.

Ok, so what does one do if these methods do not work or are not sufficient to clean the dirty lens in question?
Honestly, I say don't do anything at all. Wait and ask someone who is an expert in the field or an authority on
the subject. Some people recommend certain types of alcohol cleaning solutions, other swear by solutions
made by optics manufacturers like Zeiss. I know nothing of these things, because honestly, I do not let my
equipment get that dirty. If the brush or puff of air technique does not work for you, then you have
already broken the cardinal rule I mentioned above : NEVER LET THEM GET DIRTY IN THE FIRST PLACE. If you find
yourself with nagging doubts or questions regarding what to do in a particular cleaning scenario, then DO NOTHING
until you post here on Cloudy Nights and ask for advice.

Getting back to the cardinal rule, what are the other fundamental "rules" for keeping optics dirt-free?

1) Don't touch and don't let anyone else touch your optics.

2) Don't let anyone, and I mean ANYONE, use your equipment without your direct supervision. A fellow astronomer
can usually be trusted (take a peek at their instruments and lenses to see how they treat their stuff), but
never let a stranger touch or use your equipment without your specific guidance. If a person is one of those
types who never takes anything seriously or appears flippant about your equipment, then don't let them
anywhere near your stuff. Politely shoo them away and tell them their mommy is calling. The one time you
make an exception to this rule, you'll end up breaking rule #1 as well because the offending spaz is going to
stick a thumbprint on your eyepiece or objective.

3) Don't take your telescope or binoculars to the beach. Now matter how tempting it may seem, just don't do it.
Think about the idea : setting up your equipment in a place with a nearly-infinite supply of abrasive sand grains.
Combine the sand with wind and water, and one has a recipe for optical disaster. I set up my gear at the beach once, a few months ago, and I am still getting sand out of the nooks and crannies of my tripods. Common sporting-style binoculars and spotting scopes are fine for the beach, but keep your astronomical optics out of such minefields.

4) Never, ever, NEVER NEVER NEVER leave your equipment setup and walk away from it. You may get away with
breaking this rule if, and only if, you are : alone, have no children in the area, no pets in the area, and
no chance of anyone or anything coming into contact with your optics while you are away fetching a cold drink
or having a smoke. The minute you walk away, a Bolivian Oily Moth (the nocturnal variety) is going to fly in
and build a mucus-cocoon on your objective. If you must leave your stuff setup while you are absent for a moment,
then make sure you put the lens caps and eyepiece covers back in place.

5) Don't smoke near your equipment or let smoke come in contact with your lenses. If you are a smoker like
myself, then only smoke downwind and well away from your equipment (or anyone else's). Smoke is BAD for optics.

6) Don't eat or drink in close proximity to your lenses. Accidents happen. Drinks can splash and crumbs can
land in places where they shouldn't be. Treat food and drink like smoking - do it away from the equipment.

7) NEVER rub your lenses with any kind of "lens cleaning cloth" - dry or otherwise. Your telescope or binocular
lenses are not dime-store cameras or sunglasses, so don't use cleaning products designed for those types of
inferior optics.

8) For goodness sakes, NEVER try to remove a scratch with a scratch-removing solution! These scratch removers were
intended for use on windows other non-optical quality glass. They work by using mild abrasives to "even out" the
glass surface around the scratch, reducing it's APPEARANCE. In reality, if you use something like his on your
scope optics, then you might as well hit the lens with a sledgehammer. You will only make matters worse.

9) Finally, don't freak out if you get a small scratch or blemish on your lenses. Chances are, it may be
unsightly but it will have a minimal effect on the performance of your instrument. Freaking out over scratches
leads to well-intentioned but tragic episodes of optics cleaning - which inevitably makes matters worse.

This has been my experience with optics. It is better to be accused of being "**** retentive" or "obsessed" than
to have damaged or scratched optics. Remember, you cannot take back a scratch - it's permanent.

Ok, that's it. If anyone else can add something to this, please feel free.


#2 wilash


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Posted 01 October 2005 - 04:19 AM

Relax. Most optics are not that delicate. I have heard of a birder that licks his binos clean - probably to prevent people from borrowing them (yuck!).

#3 revans



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Posted 01 October 2005 - 09:18 AM

I have some dust on the inside of a 127mm Meade ED/APO objective lens which I can't clean. I'm afraid to dismount the objective cell because I may never get it collimated again. I was considering sending the OTA off to Meade for cleaning but is there any other alternative I haven't thought of...

Rick Evans

#4 Glassthrower


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Posted 01 October 2005 - 09:42 AM

Rick -

Does the dust impact the performance of the scope, or is it one of those things where it bothers you only because you know it is there? If it is the former, then I would see about getting it cleaned, if it is the latter then I would try really hard to forget that it is there. But if you are like me, you'll obsess over it until you drive yourself bonkers!


#5 werewolf6977


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Posted 01 October 2005 - 11:51 AM

Actually, your primary can get very dirty before it appreciably affects perfomance. It's more a matter of the area of blockage posed by the offending material. AS far as prepackaged lens cloths, the ones offered by Zeiss are an excellent product. De-dust your primary (lens) as Bebs suggests, then clean gingerly. Here's a link about optics cleaning: http://www.arksky.org . go to the cleaning page. It gives methods, and formulae for cleaning solutions.

#6 Starman1



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Posted 01 October 2005 - 01:24 PM

Cleaning lenses and eyepieces is one kind of cleaning. Cleaning mirrors is another kind.
For the first kind, see TeleVue's recommendations here.
For the second kind, see Sky & Telescope's recommendations: here.
They shouldn't be cleaned often, but when they need cleaning, these sites have excellent advice.

#7 Brian Carter

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Posted 01 October 2005 - 02:04 PM

In my experience, cleaning optics is not that stressful. I don't clean my primary more than twice a year, but I clean my EPs after every observing session. I haven't had a scratch yet. As long as you are careful, there is no big deal. I agree with the gently brushing or blowing away of particles. Afterwards I get a syringe and squirt a little unscented rubbing alcohol on the glass and then absorb it with some lens tissue. That generally picks up the last little bit of particles and disolves eyelash oil at the same time. I can get away with doing it all without rubbing the glass. If necessary a clean cotton ball will get the last little bit of smears off.

For my mirror... the bathtub and some cotton gloves work best. Set a little alcohol on the glass to disolve stuff and then rinse it off in water, let it air dry on an incline so all the water runs off. No problem.

Optics aren't SO fragile and they do get dirty and they do need to be cleaned occasionally. They require more care than Windex and Paper Towels, but not a sterile environment and perfect technique. I've been cleaning them this way for a couple years now and never a scratch. In my experience it is harder to not get fingerprints on glass than it is to scratch them.

But Rule #2 I like. My first star party was for some cub scouts. I turned away for a minute to look at M51 in some guy's TMB APO, and when I came back the kids were reaching down my tube playing with the secondary. Knocked it all out of collimation and put a bunch of sticky fingerprints on the mirror. ARGH!

#8 Don W

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Posted 01 October 2005 - 02:28 PM

Yeah really. It's not rocket science. You can clean your lenses and mirrors without damaging them if you exercise reasonable care. And the real first rule of cleaning your optics is "Do no harm".

#9 Penarin



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Posted 01 October 2005 - 06:02 PM

Some of the problem, especially when you're new to all this, is that the quick, easy fixes (air in a can, pre-moistened wipes, spit and the corner of a T shirt) are all BAD ideas.

I agree with trying to keep them clean in the first place.

And this is just brilliant:

The minute you walk away, a Bolivian Oily Moth (the nocturnal variety) is going to fly in
and build a mucus-cocoon on your objective.

I got an image of the creature from "Alien" stepping out of a large dob :)

#10 DaveO


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Posted 01 October 2005 - 11:29 PM

I was reading the lens cleaning method on the Tele Vue site and they actually recommend using Windex to clean water soluble dirt from the lens. They even use Acetone for cleaning; but won't Acetone hurt the rubber around the lens?


#11 wilash


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Posted 01 October 2005 - 11:48 PM

I have some dust on the inside of a 127mm Meade ED/APO objective lens which I can't clean. I'm afraid to dismount the objective cell because I may never get it collimated again. I was considering sending the OTA off to Meade for cleaning but is there any other alternative I haven't thought of...

Rick Evans

I am not sure how your objective cell is attached, but I had a similar problem with an M503 Mak Cass. I unscrewed the screws from the tube holding the front miniscus and removed it. Cleaned everything out and mounted the miniscus cell back on the tube. No problems with collimation.

#12 Carol L

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Posted 02 October 2005 - 12:19 AM

And this is just brilliant:

The minute you walk away, a Bolivian Oily Moth (the nocturnal variety) is going to fly in and build a mucus-cocoon on your objective.

Weird things certainly can happen to a scope.. even when you're right there. :p Before getting a Cat Cooler, I used to set my LX-10 on the deck to cool down prior to a session. One day I was in a big hurry and locked the OTA in a position horizontal to the ground and then removed the cap to the back port so the OTA would cool faster. I was right there running the wires and such, and son of a gun.. within minutes, a little Chickadee landed on the deck railing and started eyeballing the hole in the back of the OTA.
I never did that again! :roflmao:

#13 lighttrap



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Posted 02 October 2005 - 11:22 AM

Carol, your chickadee story makes me laugh. I had a Carolina wren perch on my dob, one evening while I was setting up early. They'd already made nests in each end of my overturned, rackstored canoe. No way I was gonna let that little fella stick around long enough to do any wren business in or on my scope.

Regarding optics in general, there's a couple schools of thought. Some folks don't clean them at all for fear of messing them up. Others spend so much time worrying about keeping them clean that they limit their enjoyment of the optics, unnecessarily. If you're around optics long enough, you'll figure out when and how to clean them, and you'll quit worrying about it so much.

To me, the reason I have binoculars and scopes is to use them, and I'm going to use them where I need to use them, and clean them as necessary. If that means taking some Nikon or Fuji binoculars down to the beach to look at shorebirds, or taking them out to sea to look at pelagic birds, or using them to look at the nightsky wherever I happen to be, then so be it. I bought them to use, not to obsess over.

Also, keep in mind that the effect of specs and smudges on optics has everything to do with how close to your eye the mote is. A tiny mote of dust on an eyepiece may be quite noticeable, whereas a lot of dust on the primary mirror of a reflector may not even detract from the views on most DSOs. I've been rather surprised at just how much dust it takes on various Dob primaries to really cause all that much of a noticeable effect on anything other than planets. When the mirrors do get dusty, and they will, just take them out and float the dust off with 70% lab grade pure ethanol, (ethyl alcohol) 30% distilled water in a squeeze bottle with the mirror placed firmly, vertically on a folded towel. Air dry, reinstall, collimate and go. Like Don says, this isn't rocket science.

Regarding eyepieces & binocular coatings, most of the better binoculars and eyepieces these days have remarkable durable coatings. The exception would be some of the lower end "broadband" coatings. I don't know about newer versions, but some of the "broadband" coatings coming out of Asia a few years ago were a bit on the delicate side. But, even then, just use your head. Use a soft natural bristle brush to remove everything that can be removed that way, and then if necessary lightly moisten a Q-tip in the 70% Etoh mixture mentioned above and very gently remove any remaining smudges, etc.

Incidently, DO NOT use rubbing alcohol. It's got lanolin and other nasties in it. Most pharmacies will sell you either 70% Ethanol or 100% Ethanol for a bit more. A pint bottle would be a lifetime supply for most folks.

#14 dvb


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Posted 02 October 2005 - 03:39 PM


Any thoughts on this "home-brew" solution? It is pretty much identical to what was often recommended for cleaning vinyl LPs -- although some of the "inmates" of Audio Asylum were uncomfortable about using PhotoFlo as a surfactant.

#15 Redfish


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Posted 02 October 2005 - 04:19 PM

I've thought about this matter a lot. I think the best way is to store the mirror up side down, so that dust won't collect on the surface. However it depends on your cell design whether or not this is possible. I still have to find a good solution.

#16 werewolf6977


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Posted 03 October 2005 - 05:41 AM

Excellent stuff! Have used it for years!!!

#17 mnpd


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Posted 09 October 2005 - 02:23 PM

Ever notice that optics cleaning can become an obsession....if you let it? Once you are aware that those few specks of dust on that primary even exist, you lose sleep until somehow you get that mirror looking pristine again! You turn into a version of the character that the TV show "Monk" is based on. We sometimes even feel the obligation to apologize for any visible dust that shows on the photos of optics we post here.

I've had to stop using a flashlight to "examine" the primary from the front of the tube, because the dust has already started to settle again just after cleaning. And, I not even particularly obsessive-compulsive; far as I know! :)

In practice, the only image degradation I get from dirtiness is from what gets on the eyepieces, and even then its only on bright objects such as planets. That said, just thinking about the dust that has settled on my primary makes me cringe!

#18 Norvin


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Posted 09 October 2005 - 08:31 PM

For Newtonians & Dobsonians...

Items Needed...

- 3 jugs of Sam's Choice distilled water ($.59/jug).
- 1 box of STERILIZED cotton in rolls.
- 1 small bottle of Dawn dish soap (regular unscented).
- 1 one quart plastic water pitcher.
- 1 spray bottle (kind of like a glass cleaner bottle). It is important that it has never had anything in it.

1) When you get this stuff home, wash your hands well. Rinse the spray bottle out and use the nozzle a few times with distilled water. Once you do that, fill the bottle with distilled water and put the nozzle back on.

2) Rinse the 1 quart pitcher out a few times with distilled water. Put ONLY 1 drop of Dawn dish soap into the pitcher then fill it with distilled water.

3) With the mirror facing you standing straight up so water can run off of it, spray the mirror with the spray bottle full of distilled water starting at the top going left to right working your way down 5 times. Leave the mirror wet which is fine.

4) Set the mirror down so the reflecting surface is now facing straight up. Pour the distilled water & soap solution over the mirror until 3/4 of the mirror is covered.

5) Take out your STERILIZED cotton. Wet it by pouring the distilled water & soap in the pitcher over it. Set it on the middle of the mirror. While not placing any pressure from your hand onto the mirror, move the cotton in circular motions working your way off the mirror. Do this a few times replacing and re-wetting the cotton each time you start again.

6) Stand the mirror up and rinse it off again with distilled water poured straight from the jug. Be careful not to touch the mirror with the mouth of the jug. If the water sheets off and leaves droplets, then your mirror is clean. If it doesn't, repeat steps 6, 7, & 8.

7) With a dry piece of STERILIZED cotton, dry the droplets off the mirror. You can place a very little bit of pressure onto the cotton. You should hear the cotton make a streaking sound. Since the mirror is clean of particles, it won't scratch it unless you put way too much pressure on the cotton.

8) Put the mirror back into the telescope carefully and re-collimate.

#19 Glassthrower


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Posted 09 October 2005 - 11:21 PM

Excellent stuff! Have used it for years!!!

Pete, which stuff are you referring to? The home-made cleaner that DVB linked, or the Zeiss fluid?

Any suggestions as to which liquid cleaning fluid is the best for refractors and binoculars?

BTW, I noticed there is a trace amount of dust BEHIND the objectives on my 25x100 binos....needless to say, now that I know it is there, it bothers me. But I have learned to just ignore it since it does not effect the performance to any noticeable degree.


#20 werewolf6977


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Posted 09 October 2005 - 11:51 PM

Dr. Clay's formula. Works on corrector plates, and lenses. Haven't cleaned my newt primaries yet. Might try Norvin's idea for them.

#21 gazerjim



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Posted 12 October 2005 - 02:12 AM

If you use your optics, they will get dirty.

Wish it tweren't so, but dirt, pollen and who-knows-what will eventually find its way onto exposed surfaces. A few personal observations:

-always clean your primary mirror by either rinsing it first; or better yet, immerse it in a water/soap solution and swab while immersed.
-of all the mediums I have tried for wiping coated sufaces (lenses, corrector-ugh!- plates) sterile cotton in rolls works best. Use it liberally.
-don't try to partially clean a corrector plate; it's usually an all-or-nothing affair
-no one has a precise formula for when best to clean your optics; leaning to the side of caution is good advice--especially for corrector plates. But cleaning need not mean the death of your optics
-for the stubborn who-knows-what stuff that likes to smear instead of leave, I've had good results with ROR. I'm sure there are other fine products. All gunk is not created equal, and alcohol may or may not work.


#22 Guest_**DONOTDELETE**_*

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Posted 13 October 2005 - 12:38 AM

Whilst great care must be taken in the cleaning of any fine optical surface, I also like to imagine that delicate optics have memories. That is, they hold a record of all previous cleanings. And unlike our own memories theirs are permanent. You may not detect anything with your naked eye; the results of careful cleaning are microscopic. Therefore as important as meticulous cleaning methods are, I believe infrequent cleaning is just as important.

#23 Joad



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Posted 13 October 2005 - 10:28 PM

One man's experience doth not a valid generalization make, but if anyone would have ruined an SCT corrector plate by now, I would have, if such optics were terribly delicate. I polished mine with an eyeglass cloth when I bought it used last spring--before I read that I wasn't supposed to do that. I didn't do any damage then, and I went over it with a magnifying glass and flashlight. Since then, pine pollen and my general obsessiveness have caused me to use the distilled water/alcohol/cotton ball technique a number of times, and I still haven't ruined it. Every time I have bad seeing, I blame myself, then a night like tonight comes (I'm on a lunar viewing break) and the scope is performing like a champion (proof: I see the central craterlet in Plato as a steady sight, and a second craterlet is blinking on and off for me--I've never seen the craterlets so well, and they are very tough to view). Later I'll go for Mars with my new red filter. I hope I get better views than my last time out.

But I digress. My point here is that I've had the dickens scared out of me by reading how delicate optics can be (and I wouldn't touch my mirror for anything--that's a whole different matter), but I think those who have more reassuringly suggested that the optical coatings are pretty tough are probably right. No reason to get careless, but, for the beginners among us, I don't think you need panic if you need to clean your optics. Do be careful though.

#24 StarsAbove


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Posted 05 November 2005 - 08:35 AM

I'm going to add my two cents for what it's worth. I too went to the school of "never clean your optics unless you absolutely have to". I think with the advent of modern coatings that at least lenses are multicoated with extremely hard coatings. As long as you blow the dust off before cleaning, you should be okay as long as you take care.

I purchased some Zeiss wipes originally and dried my corrector with sterile cotton. That was okay but when I got some nasty film of the corrector it was insufficient. I know there is much advice on cleaning solutions out there. But I decided that the manufacturer probably knows best. So I followed the Celestron solution of: 60% distilled water, 40% isopropyl (I use 91% concentration) and one drop of Dawn dishwashing liquid per quart. I apply this with sterile cotton. I buy it buy the roll rather than the balls. This worked great to clean the haze of my corrector. I change cotton frequently for drying the lens. Looks almost factory clean when done.

#25 Gordon E Reade

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Posted 08 November 2005 - 02:32 PM

Some very very good advice but there is another approach to the problem. I take my Questar 50th anniversary addition to as many as a 100 public events a year. Sure kids often grab it before I can ask them not to. People have been known to eat or drink or smoke near by. Once it was even tipped over.

I treasure this scope and I don’t want to see it damaged in any way shape of form. But at the same time I want to use it and share it with other and so I have decided that someday I’ll sent it back to the Questar Corporation to have it restored to new condition. There is nothing in or on the scope that can’t be repaired or replaced. I suppose a complete restoration will be expansive but that’s not the point. The point is public astronomy programs are what I want to do with my life.

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