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Message: <blockquote data-quote="Binastro" data-source="post: 3327752" data-attributes="member: 111403">I have been using magnifications of 80x to 100x for terrestrial viewing for almost 60 years. Mostly long focus refractors and Maksutovs of 70mm to 150mm aperture. Also 53x and 25 to 40x drawtube scope.Distances typically 1 mile, 4.7 miles, 11 miles, 12 miles and 20 miles.It is only at 45 miles that the images of distant sea cliffs have been very poor. Here lower powers are better.At 20 miles looking at ships the detail is good, but often accompanied by the same ship upside down due to very common mirages.The fortresses in the Thames estuary show excellent detail at 12 miles.Sometimes viewing through selected glass windows improves the views. This negates local heating effects.Clearly my Seeing conditions are better than some. I choose my time and place carefully and also suitable weather.I also regularly followed high flying aircraft up to 200 miles distant. Sometimes 350 miles total from near one horizon to the other.The Celestron 20x80 binocular shows excellent detail at 11 miles.I cannot think of many occasions when 20x60, 18x50 and 30x50 binoculars have been seriously affected by poor Seeing.Temperate climes have their advantage.</blockquote>