Birding question ??

Is there a simple device I can insert to provide a correct image view through my Pronto 70mm refractor without involving a 45 or 90o dia. ? I would like to view straight through like a like a spy glass.. would appreciate any advice, I thank you and so do the Bald Eagles around my property.. JM

I'm not sure... try posting this in the Birding forum. They do lots of that stuff there . Plus someone may chime in here.

A few companies (incl. TV for the high-end and Bushnell at the low end) sell porro prism assemblies (like the ones used in some binoculars) for 1.25" eyepieces; they're a little bulky and have a lot of elements to introduce scatter and aberrations, but they work. There's also a 1.25" Vixen straight-through erect image adapter that's a little cheaper than the TV version; I'm not sure how well that one works.