The idea of attaching a "doubler" to a
binocular, as seen in the
Swarovski doubler or
Bushnell Universal 2.5x to increase its magnification is not new. Amateur astronomers, myself included, have held monoculars and magnifiers to one of the eyepieces of a tripod mounted astronomy binocular for many years. I commonly use a
Zeiss 3x or even a
Nikon 5x15HG behind my 10x70 binocular when mounted on a tripod to increase magnification when I want to split a double star or to check an ID on a small object. A tripod is essential, of course, and I also recommend a tripod for people who attach a
doubler to a
binocular or, failing that, to at least support the binocular on a nearby object. High magnification turns a handheld binocular into a wild, bucking horse.