Yellowstone is where I would like to have more upcloser power. I have a D3100 and Nikon sell an adaptor you put between the body and a scope. Nikon also has a scope, $2000, with an 82mm lens in front to bring in lots of light. This is all mounted on a tripod of course. From what I've been able to gather on the web there are two concerns, hard to use on fast moving objects and difficulty in focusing. I've seen some digiscoped photos on-line that were absolutely breathtaking. It's hard to find good info about this use of camera/spottingscope. I just can't justify $5 to $10 K on a telephoto lens. If I was a professional, well, maybe.
Right now my upclose power is with a 300mm zoom. I need more. An suggestions on how else to accomplish this, with fairly good quality, for under $3K