About this "external fogging..."
I once made the error of keeping my rifle in an air conditioned camper with me overnight, and ran the AC hard enough to keep it at about 67*F. I left the camper with rifle slung the next morning as the sun was peeping over the horizon. It was about 80*F that morning and muggy as can be. I hadn't walked a quarter mile when I saw a coyote out in the wheat field, maybe 200 yards out. I had him dead to rights. When I raised the rifle to aim, my scope was entirely fogged up and I couldn't have hit him from fifteen feet away. This was about four years ago.
I don't know external fogging can be avoided except that I believe (am I mistaken?) I have heard of coatings that are reputed to do just that. I can't imagine that it's 100% effective, though.
Oh, yeah...the scope this happened to? It was a VX-3 or VX-3i.
