Well I was playing with my 5x WF microscope eyepieces when I decided to figure out what the focal length was.
It's LOOOONG - about 50mm! And it's a classic Huygens.
I need to find an 0.5mm or so thick bushing to use it in a classic scope though - it's 23mm and I want something more elegant than tape. Actually a C-shaped tube of thin-walled copper would make for a tight fit. It should be 30 mils. Brass would be good. Can you buy brass sheet?
The AFOV is about 30 degrees, but that doesn't really bother me. With a 50mm eyepiece pair in a binoviewer you would get spectacular lunar views of absolute crispness in a long refractor. 50mm/16 = 4mm exit pupil even in a classic 76/1200mm scope, and only 24x.
Anyway a 5x microscope eyepiece provides an excellent route to very low power views in long refractors.
-drl