That is asking a great deal of any binocular
if you expect to actually see details on a sky diver or even a parachute at that distance of nearly a mile. Handheld binoculars
simply won't give you enough magnification to see that level of detail, but I would at least borrow a conventional 10x42 or 10x50 to see how it works. I suspect you will need more magnification. Going to something with higher magnification - an observation binocular
or spotting scope
- though, will require you to use a tripod
for the sake of steadiness, but then you have tracking issues as far as following a moving object.