I use one of those scope LensPens by Leupold. It came with the scope I ordered and it works great. Before that I used camera lens cleaner and paper. I still do, it I get mud and muck on the scope (which is often), then I polish it with the lenspen.
You ever seen those little kits sold in photo equipment stores that contain a fine brush, little sqeeze bottle of solvent, and roll of funny onionskin-like papers? Well, that's what I resorted to using when my piece-of-**** Leupold lens pens started mukking up the scope glass more than cleaning it! These kits work great! But don't overdo the solvent.
In my chosen profession (Clinical Lab. Technologist) we do a lot of work with microscopes, and over the years i've found that, believe it or not, saliva is a good lens cleaner with a soft cloth or lens paper.
Jay, that acetone might be a mite rough on some lens glues/seals.
As you know, proper cleaning and maintenance are important parts of obtaining the optimum level of performance from your riflescope.
Lenses: scope lenses are coated to reduce light reflection and light absorption. They should be cleaned as carefully as you would clean a camera lens. Use a lens brush to remove dust. If the lens is dirty, clean with pure alcohol, a grade of pharmaceutical acetone (keep it off of wood stocks), or pure water on a cotton swab.
Clean the lenses as you would a fine camera lens. Use a lens brush to remove dust (or simply blow off the particles). Fingerprints and smudges that cannot be removed by brushing can be removed with a good grade of glass cleaner. For example, Leupold uses a pharmaceutical grade of acetone for 99% of their lens cleaning. Use a cotton swab for application of the cleaner directly to the lens. Shake off the excess acetone so that it does not drip. Start in the center of the lens and work the tip to the outer edge of the glass. Use as frequently as necessary to keep the lenses bright and clean.
I am a professional photographer. I use Carl Ziess lenses that cost $3500+ for 1 lens. I learned the hard way how to and how not to clean coated glass.
1. Use a strong bulb shaped blower to remove the dust etc. from the lens while holding the lens to be cleaned up side down. This can be bought at a camera store. Get a big one.
2. While holding the scope up side down use a natural hair brush to clean the remaining dust. These can be found at WalMart in the makeup department. I suggest getting this late at night so your friends wont catch you shopping in the makeup department.
3. Use the blower again.
4. I do not suggest lens tissue it is too ruff on the coatings, and it leaves little fibers. Get an old 100% cotton tee-shirt that has been washed about 50 times. The 50 or so washings will make the cotton soft. Wash the tee-shirt again with NO detergent in hot water to remove any detergents that were left from the last washing. Cut it into pieces about 5"x5" and store in a zip lock bag. Do not use the under arm section of the tee-shirt, it may have deodorant imbedded in the fabric.
4. Use your breath, blowing on the lens making a haaaaa sound to fog the lens. This will get it wet (fog). It's OK if you have been eating onions the scope won't care. Use lens cleaners ONLY if the lens is EXTREMELY dirty. I suggest never using lens cleaners because they are destructive on the lenses coatings. Pharmaceutical grade acetone may also be used but, I wouldn't make a regular habit of it either.
5. After the lens is fogged with your breath, gently clean with the piece of tee-shirt using circular motions starting in the middle and working your way to the edge holding up side down. Remember the key word here is gently.
6. Repeat the last 2 steps as many times as needed to get the lens clean.
I have a few different lens cloths that I use. The ones I like most are the 50% Nylon, 50% Polyester. These were reccomended by Canon when I got my L series Lens and I use them on my riflescopes too. I think the type of cloth you use is going to change depending on the type of lens and brand of scope. Generally, lower end scopes don't have the real cool high tech coatings on them so they're a little easier to clean. The paper lens cleaning tissues would suit me just fine on them. On a coated lens, you couldn't pay me enough to put any tissue on it. Paper in general is abrasive.
As for the solvents. I've never seen any maker of lenses use harsh solvents. While several people here say they are recomended, I hadn't seen that and own some of the brands mentioned. I'll have to check that.
NEVER use stuff like window cleaner. I HAVE see where vendors state that window cleaner is harmful to some coatings. I steer clear of that. It also will never clean up. The cleaning solvents mentioned above are all an ultra pure version of the product. Alcohol needs to be very very pure to not leave a residue on the glass. I can buy into the saliva thing if you have a nice lens cloth since that will generaly come off completely. (lest your eating gummi fish or something).
I think I'd rather use a $15 5" square cloth than a shirt piece. My scopes and lenses generally cost enough that I'd opt for something I was sure had no foreign fiber in. While I'm sure some cotton shirts would be just fine, I'll get a lens cloth.
Head to a camera store and get something that they reccomend for high end glass. You'll be amazed how nice they clean and how fast. I'm just happier that the real nice lens cloths clean so fast I don't have to sit there rubbing forever. Less rubbing = less chance to drag dirt on the lens.
I usually clean my lenses dry. And, the best way to clean lenses is to not get them dirty. Get nice covers and use them. Most of the dirt I see comes from storage when not covered and I'm guilty of that myself on my cheapo 22's and such.
When I took microbio in college the professor who was VERY anal about his microscopes advised us NOT to steam up lenses with breath because H20 and CO2 (we exhale both) react to make H2CO3 which is carbonic acid and very tough on coatings. Just hought I'd pass that on. I use a brush from a lens pen then use Kodak paper and lens sol'n.
I use a 12"x12" Silk cleaning cloth from Oakley. Their Iridium coatings on their sunglasses sctratches very easy and shows everything. This cloth wont scratch them it sure isnt going to scratch a scope lens. I first use a bulb blower and brush it out, the solvent I use is Zeiss (you can get it from Cabelas) and spray a fine mist in the air letting it settle on the lens. Then using the silk cloth I polish it up nice and soft. Then I put the lens covers (Butler Creek) back on. All my optics look as new as the day I took them out of the box.