The problem is in exit pupil - this is the diameter into all light collected by objective lens is put through.
the formula is:
De = Do/mag
where:
De - exit pupil diameter
Do - diameter of the objective
mag - magnification
It doesn't make any sense to have this diameter much larger than 8mm (maximum diameter of the human eye iris) because the light outside this will not enter the eye anyway.
For magnidfication of 2.3x the diameter of the objective is 18.4mm... anything wider is a waste of aperture.
more here:
http://www.nikon.com/products/sporto...c/basic_05.htm
Also, you have to consider the fact that photographic objective lens i designed to have flat focal plane.. while eyepiece is designed for curved focal plane, produced by telescope lens.. and another issue - eyepieces are designed for much slower objectives.
I tried something similar a long time ago but gave up.