Originally Posted by Robf
clean grease free glass mists up a lot slower than dirty glass... the quickest way of getting it to attact mist is to wipe it with your fingers... finger grease is hydroscopic, which means it attracts moisture...
a clean with a proper lens cloth and solution and scopes will mist up a lot less... a microfibre cloth it a good 1/2 way house, but your need to make sure it and the lens is clear of grit/dirt, otherwise you can scratch it, or certainly abraise the coating.
Just what I use Rob but there have been occasions, Newbury springs to mind, where I was ankle deep in mud & soaked through but noticably steaming as well ,no glass will resist that. I even put my specs away as they were achieving bugger all. Mid range shots were still achievable with hold over on X10 even though I had to be told where to point the muzzle!