See below. This is the cleaning method from a local scope guru here in Christchurch NZ. All but retired from all business now but used to repair and service scopes back in the day. Apparently if asked to stock a certain line of scopes from an agent he would pull the scope to bits and have a look to see if would be ok.
Copied it from his website a while back just in case it disappeared
"Now that you own a fine set of optics, you should learn how to keep them in the best condition possible. One careless cleaning is all that it takes to scratch the lens coating and lens surfaces. Those scratches are PERMANENT! You don't get a second chance.
STEP ONE. This is the most important part (omit this and scratches are a certainty). Using a clean, stiff-bristled brush (pig bristle not synthetic), such as a 12mm high quality paint brush, work around the exterior lenses using a flicking action to lift off all traces of grit and dust. Don't worry if smears now appear on the surface: step two will take care of them. Blow hard on the lens to remove any loosened material. Examine the surfaces closely. Only when you are certain that no dust or grit remains proceed as follows.
STEP TWO. Select any of the following: Cigarette lighter fluid as used in "white-spirit" stoves; Clear alcohol; Methylated spirits; or proprietary lens cleaning fluid but not an ant-fogging solution. An interesting aside here: the CEO of Burris, when asked what solvent they used, told me acetone. Now, I too use acetone for many particular jobs, including cleaning of isolated lenses. What I must stress is: do not use acetone on your scope, binocular or cameras lenses because it can, and most probably will attack the seals or any plastic bodywork around the lens you are attempting to clean. Use one of the following (in descending order of preference: Commercial micro-fibre lens cleaning cloth; Commercial LENS tissue ( but not any substitute tissue such as toilet paper because there may be harsh fibres and/or high ash content incorporated); or flannelette pyjama material which MUST BE OLD so that all harsh fibres are long gone during the process of laundering. I repeat: Do not use toilet paper. Moisten the cloth or tissue with the approved solvent. Never pour fluid directly onto lens. Working quickly and gently, rub all over the lens surface before solvent evaporates. Select new tissue or fold cloth to a clean, dry part. Next, breathe onto the lens surface. This deposits, momentarily, a mist of distilled water. Wipe lens again, lightly, with a new tissue or dry part of the cloth.
JOB DONE - CLEAN LENSES.
SOME ADVICE. It is inevitable that foreign matter and raindrops etc. will accumulate on lenses when away in the field. Please RESIST THE TEMPTATION to use the shirt-tail or toilet paper on the spot. The particle of grit you didn't see under that raindrop will leave its calling card to remind you of your mistake from that time on. It is better to put up with temporary inconvenience than permanent reduction in optical performance. Solution? Well, DON'T RUB. Personally I will suck the corner of my handkerchief and then soak off each raindrop by capillary action. This may leave some watermarks (which will be taken care of on my return home) but makes the unit useable again with the precious lens coating undamaged. Snow is a great problem: get it off the lenses immediately. Try blowing it off with your breath. If you leave it on riflescope lenses it is very likely to cause sealing failure and a fogged-up scope. I hope this helps you to get the best out of your optics.
My final words on this subject concern Lens Pens. These have become very popular overseas with many writers extolling their effectiveness. At least some of these devices use a graphite powder to polish the surface. My feeling about them is negative for one simple reason. The cleaning surface is small and not cleanable in its own right. It will inevitably pick up dust and grit when being used, and, unlike a lens tissue which is used and then disposed of, or a micro fibre cloth which should be washed carefully and often, the lens pen will be overused until it causes the inevitable scratching. Then, it will be too late."
