ScopeCam
thingiverse
Cut out transparent plastic to shape of reference. Attach to scope, and put Gopro Hero 5 on top. Gopro will now reflect off plastic and see what you see. This model is specifically made for Gopro hero 5, feel free to modify it.
Download Model from thingiverse
With this file you will be able to print ScopeCam with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on ScopeCam.