When you are looking at binoculars...?

Question

...there are usually 2 numbers like for instance 5 x 40, the magnification and the objective diameter, but what means when there are 3 numbers like 20 x 60 x 65??

thanks

Answer 1

The last number refers to the magnification. It will have a dial that will increase the magnification to 65 times.

But remember, if you want to use these for astronomy, then it will be the objective diameter that is important. More light=better views (all things being equal of course)

Answer 2

Zoom binoculars show two numbers for magnification.  Minimum and Maximum.  It's very odd, though.  And i shy away from zoom binoculars.  The zoom adds huge amounts of cost, and usually, they compensate by making the whole thing cheaply.  So it's expensive, but not very good.  There are binoculars with interchangeable eyepieces, like on astronomy telescopes.  It's not zoom, but the magnification can be changed, and there is no compromise for quality.  You do need two eyepieces of each magnification, and they must be carefully matched to each other.

So i have some 8x21 binoculars.  8x magnification and 21 mm aperture - not very big, but they fit in my pocket.

I've started talking about my 240x254 monocular.  That's a 10 inch telescope with an eyepiece that yields 240x magnification.  But since this isn't customary, it leads to confusion among the old timers.  I started doing this after i'd given a few introductory courses.  I'd talk about your eyes (1x7 binoculars), my small 8x21 binoculars, a 22x60 monocular spotting scope, and finally the 240x254 monocular telescope.  It just seemed to make things more comparable.

And, i might get a binoviewer for my scope, making it a 240x254 binocular.  That would be even more confusing, as you can really get twin telescopes - each 16 inches - in a binocular setup.