I have a Tasco # 634V 3 X 9 riflescope that I bought 30 + years ago. The owners manual is long gone. Ive never had a problem with the focus until now. My eyes are getting old and now that I wear glasses targets are getting a bit out of focus. Is there a way to adjust the focus? I see a setscrew(?) right behind the power adjust ring and just in front of the Ocular bell / eyepiece. Im thinking if I loosen it the eye piece can be rotated to adjust the focus but since the scope has never given me a bit of trouble I dont want to just start turning screws without knowing what they are fore.