Zeiss makes a small pump bottle of scope cleaner. Anybody with a quality scope should definitely own a bottle of it(it is not that expensive). I do not know what is in it, but I do not care what is in it. If you have dirt or mud all you need to do is spray a couple of pumps, wait a minute for it to dissolve the dirt-or dust-or whatever. Then use a can of compressed air to blow everything. off. Repeat this procedure. Then spray a little more of the liquid on your scope and clean with lens cloth. Your glass will be perfectly cleaned, perfectly clear, and no scratches. Scopes are far too expensive not to take care of them.
I bought a bottle 5 or 6 years ago, and I still have over half of it left. And I also clean the scopes of a few friends. If you were conservative with it(I am not) a bottle would probably last a lifetime. I also use one of the Leupold lens clening pens, but I only use the brush end, I do not use the rubber end. Tom.