The Nikon Lens Scope Converter is a rare accessory that attaches to the back of Nikon lenses, turning them into telescopes. You can sometimes find them listed on eBay for around $230. They’re designed for AF D-era lenses that have mechanical aperture rings, but you can “hack” your G lenses to be compatible by using a piece of plastic to keep the aperture blades in the open position.
Furthermore, you can mount the convert onto a Micro lens to make a microscope. Use it on a 105mm Micro lens, and you’ll have yourself a handheld 25x microscope!
Image credit: Photograph by Fabrizio Belardetti and used with permission