N hemispere binoc w compass not working in S?
I will admit to my ignorance here. At first, I was going to reply that there should be no difference. Before posting, I decided to do a google search (amazing what you can find) and discovered that YES there is a difference.
In general, it comes down to using counterweights on the needles in compasses to account for the force which pulls one end of the needle down (toward the earth''s center). The vertical forces are opposite in the hemispheres and so different balancing is used.
I did find, however, at least one manufacturer that makes a compass which is claimed to work fine in either hemisphere. Also note that most of the references did not speak to binoculars specifically, but apparently they are affected, too.
Thanks for postng that question; I learned something.