As for scopes here is what little I know about glass. You want the clearest glass that you can get, don't worry about the magnification. There are people that shoot iron sights out to 1,000 yards. You only need 4-9x to make it out that far.
How do you tell clear glass? Price for one. Zoom for another. Something that is common across all lenses that are zoom is something called Chromatic Aberration (linked below). What happens is that the different wave lengths of light bend different amounts when they enter the glass. This leads to a fuzzy image. Zoom lenses (variable power scopes) suffer from it more then fixed power scopes and it will be worst at the high and low ends of the range (especially the high). What it looks like is a red tinge on the upper left, easier to see is the aqua/blue tinge on the lower right (see image below) along something that has a hard edge. If you are at a store looking at scopes, take the scope, turn it to its largest power, aim it at the white ceiling some ways away were there is a color change (light vs shadow) or at merchandise some ways away (scopes close focus distance tend to be at least several feet away). There may be a knob for focus, use it to get the image as close to in focus as you can. If it looks a bit fuzzy, try a different one of those scopes. If it is still fuzzy, DON'T BUY THAT MAKE AND MODEL. Some of the example scopes that are sitting out have been dropped or banged, and are not any good anymore.
You try to find something with a sharp transition (white to black) because our brains actually suck pretty badly at telling small amounts of Chromatic Aberration. So you find the worst case scenario and do the test. If it passes that but still looks a bit fuzzy, it could still be Chromatic Aberration, or poor construction tolerances, or the glass could be ground incorrectly, or the glass or glass coatings could be crap.
So in short buy good glass or you will be pissed off, and it will give you a headache to look trough. This is the same for camera lenses.
http://bmayer.blogspot.com/2005/01/aber ... -snow.htmlhttp://en.wikipedia.org/wiki/Chromatic_aberration
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