It turns out the in the “old days”, when we still had aperture rings on our Nikon lenses, Nikon used to sell a something called a Lens Scope Converter. These lens scope converters were used as an eye piece that can turn any lens into a telescope.
(Imagine harnessing the power of a Nikkor 600mm f/4G for your star gazing pleasure)
Sadly , LSC has been discontinued and it can only be found on “second hand” sites like ebay (there is one selling right now, check out listings here).
Sadly , LSC was designed and sold in the Nikon AF-D Lens era, which means that it is only compatible with lenses that has aperture rings. (For some odd reason, Nikon G lenses have their diaphragm close when not mounted on a camera, and a small flange on the bio-net keeps the blades open. If anyone know why it is designed like that please let us know. AFAIK, Canon lenses are always open).
Well, we are here with some happy news about that. Fabrizio Belardetti over at Nikon Rumors shares a quick and easy hack that can add the needed flange for Nikon G lenses so they be used with the lens scope adapter.
That takes care of the second sadly. Now that is left is to get a converter. Nicely enough, if you mount it on a fine macro lens you end up with a microscope.