Jerry 'focused' by using auto focus. He did not try again and again to get it correct!
Smart guy but lack of real evaluation. I did not get very good results until I built a stepper focuser for the lens. Then I found out how good it really was.
See here
http://members.optusnet.com.au/~avan...AGLE&OMEGA.jpg
and here
http://members.optusnet.com.au/~avandonk1/COR_AUST.jpg
Here is an animated gif, each frame is 0.1mm linear movement of the focus ring
http://users.bigpond.net.au/avandonk/s12.gif
Bert