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Message: <blockquote data-quote="typo" data-source="post: 3148693" data-attributes="member: 83808">I think I need to clarify some stuff.I suppose most will have heard of 20/20 vision (though it is usually referred to as the metric 6/6 in Europe). It is the upper limit for what is regarded as 'normal' vision. Statistically most people do a bit better than this, though of course not everyone. The eye test chart that everyone will be familiar with has specially designed letters or patterns that differ by 1/5th of the height and width. The size of that 1/5th is calibrated for the reading distance. On the 20/20 line of the chart that difference creates an angle to the eye of 1/60th of a degree which is usually referred to as an arcminute or 60 arcseconds. A small percentage of people will have eyesight twice as good as 20/20 which would be 20/10. There have been very rare examples of individuals recording 20/8.What is very confusing is that the one arcminute standard used by the eye docs for the resolution, or acuity of the eye is not the same measurement used by everyone else when measuring resolution. If you use stars, MTF or the line charts we tend to use here, the results are numerically a factor of two greater. So 20/20 becomes 2 arcminutes or 120 arcseconds and 20/10, 1 arcminute or 60 arcseconds.The first three sets of comparisons I reported here used a USAF 1951 line chart, and I was testing the effect of shake on the detail I could see. So testing my eyesight or apparent acuity. The best result was 60 arcseconds (20/10) though this was with two eyes which is usually a bit better than the single eye figures your eye doc would give you. I also listed the resolutions for the binoculars with the objective stopped down to 20mm. The magnification was boosted with another binocular for that measurement.The last report was an attempt to replicate the observation made by Binasto. Although I calculated the size of the spots as an angle, the results should not be compared to the other studies in any way. Seeing a single feature is quite different from resolving two or more spots or lines, though highly dependant on contrast and other factors. About the 'biggest' star you can see in the sky is Betelgeuse and that is 0.05 arcseconds or an angle 150 times smaller than the smallest spot I was using and you don't need a binocular to see that.David</blockquote>

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