I can confirm that insect repellants totally stuff optical coatings. Last year at Snake Valley someone sprayed repellent near my Tak, and it destroyed the coating to the point I had to send the scope back to Japan. They were initially going to just remove the old coating and re-coat, but apparently the glass was damaged and the objective lenses had to be replaced totally. $6000.00 was the final cost including all the freight. Luckily I had all risks with my Insurance. So as far as I am concerned, any repellents used at least spray types do NOT belong anywhere near sensitive optical coatings.
