This may not be the coolest looking telephoto lens mod out there, but it just might get the job done. It only requires a bolt, some cardboard, a few twist ties, and binoculars. I am not sure this will hold up to moving around, but for that one telephoto shot you want to make, why not give it a try? – Link
Related:
DIY Telephoto lens – Link
Webcam Telescope from MAKE Volume 2, page 135 – Link
