I have a varixIII scope (from the EE) that has an objective lens that is dirty. I just tried one of those "lens pen" things, I guess it helped, but it looks like it needs a cleaner of some kind. Is it OK to use Windex, or alcohol or something to clean it?
Get a lens cleaning kit for a camera. they work very well.
First, brush away loose particles.
Then apply a couple of drops on the lens surface, and using a lens tissue, wipe or touch or fondle gently in a circular motion starting fromt the center of the glass to its edge. Try not to use a bunch of cleaning fluid, but any excess will eventually evaporate.
(Acetone works really well, but first get rid of particles on the glass. Particles when rubbed into the glass will put micro-scratches into the coatings.)