A Guide to Lunar Observing Filters
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Figure 1 – A lunar observing filter helps reduce the glare when observing the moon visually with a telescope. Image credit: Flickr/Longhorndave.
1. Overview
Precise scientific measurements show the moon reflects, on average, about 12% of the sunlight that falls upon it. That makes it, on average, about as reflective as an asphalt driveway. But if you’ve ever looked at a thickening gibbous moon through even a moderately-sized telescope, it can appear uncomfortably bright to the dark-adapted eye. That’s why many visual lunar observers and lunar imagers consider filters to reduce the brightness and glare of the moon so they can see finer detail during a long observing session.
Moon filters are useful for scopes of as little as 80mm aperture, and they are essential for