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Message: <blockquote data-quote="Binastro" data-source="post: 2756121" data-attributes="member: 111403">. The differences may be because the magnification in the binocular often varies across the field.Many binoculars have a sudden change of magnification at the edge of the field especially with distortion free eye pieces.Then you have eyepieces such as those in the Nikon action VII and in the 15 x 70 revelation that have aspheric elements in the eyepieces.As you pan across the field the magnification constantly changes in an undulating fashion.I presume the aspheric element may be a plastic component fused or cemented to a glass component or possibly the glass can now be ground or possibly moulded into the complex shape.So how you would actually calculate the fields is difficult to know.In addition, magnifications are often not exactly as stated so again I'm not sure how accurate the calculations are.For me when I look through one barrel of a binocular the apparent field of view is different with each eye. This may be because I have a difference of 1.5 dioptres between my two eyes.So what I do is alternate between the two barrels and my two eyes. and then do the same for another binocular so I can directly compare the apparent field of view in the two or more binoculars that I'm testing.Of course the easy way is just to multiply the supposed magnification by the real field of view which is easily found by reference to separations of reasonably bright stars.The results are not perfect but they suit me and I do know that with strict calculations the apparent field of view will be smaller than with a simple calculation. A further complication is that I believe that the magnification of a binocular varies depending on whether you are shortsighted longsighted or neutral. And it may also vary depending how far your eyeball is from the eyepiece.So I think the best method is a hands-on approach between two or more binoculars and just see which binoculars have the widest field of view if that is important to you.It is to me as I value a wide or very wide field of view.</blockquote>

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