In article <31A0C4CC.667A@om.cv.hp.com>, greg_may@om.cv.hp.com says...

>When I was in Tokyo recently, I noticed an interesting ad. It appeared
>to be an adapter that coupled to the back of a telephoto lens and
>converted the lens for use as a spotting scope. [...]

Nikon made an excellent one (10X whatever lens it is put on, which
makes a small 135mm f2.8 into a compact long viewing scope). I bought
mine for about $50 new. There is a new one in town at a camera shop
for about $100 - e-mail me for more details, if interested.
Hope This Helps