Binocular Magnification Explanation
Binocular magnification numbers can cause a lot of confusion. Once you grasp the meanings of the digits though, choosing a pair for your specific needs is simple.
If you will be using your binoculars for birdwatching, you will need a pair with a large field of view. This will give you a large viewing area, which will make it easier to track a bird in flight.
Astronomy binoculars will have high magnifications, but a very small field of view. This will be better for zooming in on stars and planets.
The magnification of binoculars is given first, i.e. X8 X10 X12 etc.
This is the number of times the object being viewed is magnified.
So an object that is 100 metres away, will appear to be 12.5 metres away if viewed through a pair with X8 magnification, 10 metres through the X10 pair and so on.
The second number usually stated is the size of the objective lens in millimetres.
The larger this number the larger the field of view. But also as this number increases, the more the natural shake in a persons hands will be magnified. so very large lenses may require a tripod to steady them.
So an ideal pair of binoculars for astronomy would be a pair of 10 x 50. These should be mounted on a tripod and on a clear night will give great views of the universe.
An ideal pair of birding binoculars would be around the 8x32 range. These give a good vield of view and will be light and manageable.