150mm f6 45º ED APO interchangeable eps 25-60x binocular in a very good tripod with fork mount but with crank elevated center column.
The Eps should have a wide angle design of aprox 70º to 80º AFOV and an external barrel size of 55mm or less to be really comfortable with an ER of 17mm, my favorite.
And of course, how about this setup in the 20 lbs range...
I'm sure the last weight wish is the harder one

and also the less important for me.