I've used Isopropyl for years without any damage to lens coatings; on occasions I also use Acetone to remove stubborn deposits that aren't removed by Isopropyl (need to not let acetone touch anything other than the glass). It's better to disolve a deposit with acetone than to rub hard with Isopropyl.
Eyelash oil on eyepieces should be removed as soon as possible. Objective lenses that get dewed should be cleaned occasionally since contaminants in the atmosphere damage coatings. All IMHO.
|