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I test bino coatings on Luna, if there are reflections then they are not so great, if not they are fine. Now just because there are some reflections doesn't mean the bino-s are un-use-able either. Many of the cheapie 10x50 under $20 binos do a fine job of sweeping star fields and general DSO observations, yet give reflections on Luna.

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I think checking for internal reflections by observing the moon would show you reflections in almost any binocular. Some of that would be due to reflections off of the internal glass surfaces, even fully multi-coated surfaces. But some of those reflections could originate from poorly blackened internal barrel surfaces, shiny edges at eyepiece field stops and either poor or no baffles. The light from the moon is so intense, it will cause all these things to show up. It could be a number of things and it would be very difficult to separate them.

It could very well be that the majority of the reflections from the moon are there just because the light from the moon is so intense. Just about any internal glass surface, even with only 0.5% reflectivity, is going to reflect a small portion of the intense light from the moon.

Keep in mind, the light reflected internally from a full moon (approx mag -12), (even if only 0.25% of the light, the amount that might be reflected from a fully multi coated surface), is still about mag -4 or -3, brighter than the brightest star in the sky.

So part of what is going on when you see reflections of the moon internally may not be indicative of poor coatings. Even the best coatings cannot overcome that kind of intense light. It would be nearly impossible to suppress reflections from an object so bright.

edz

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