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Message: <blockquote data-quote="Kevin Purcell" data-source="post: 1562013" data-attributes="member: 68323">The lens do have a hydrophobic coating on them (that's a bit more delicate than the usual oxide AR coating that's underneath that so don't rub too hard with a cloth. The endurance test I've seen described is how long they last when rubbed with a rubber eraser which is rather tougher than the normal treatment they get.)The usual "don't scratch the surface" caveats apply.I find the easier way to clean off the accumulated gunk is: blow the surface to remove all hard particles then to rinse the lenses in slow flowing water. Then clean my index finger and use my index finger tip and a little liquid dish washing detergent (the cheaper ones work better ... avoid ones with siloxanes that give a "squeaky clean" sound). Then rinse a couple of times with slow flowling water. Shake off the remaining watter and dab off any water spots.Comes up as good as new.The dielectric mirror coating is on the roof prism's mirror surface and improves reflectivity, over the silver mirror coating, away from the deep red end of the spectrum. It's most noticeable improvement in reflectivity at the blue end of the spectrum.</blockquote>