It goes without saying that high quality is going to give better results, but also, Canon now put image stabilisation into some of their binoculars and when looking straight overhead, this is somewhat handy. Go and try a pair at the dealer.
Failing that, either some astronomical binoculars or spotting scopes have big, bright objective lenses and often, good eye relief as well. Still is best to try them though, so that you can see what suits you best.
Conan