canon sigma 2x screen mag focused.jpg:
Canon 5DMk3 Sigma 600mm lens w/Canon 2X teleconverter ISO2500 f/36 1/200sec (Canon automatically sets the f stop to f/36)
Used camera live view with maximum magnification for focus. Focusing this way was extremely difficult. I was NOT able to focus the Canon camera using the Kowa spotting scope to get any photos worth saving.