i'm learning on the fly here bob but here is what i have done, i had a second look at the ronchi this evening, the lines were bending away from the center toward the edge,i had notced on my last night of polishing that the very edge of the mirror was polishing out, mabey 1/8th inch at most. (that was what got me wondering,and why i got up in the middle of the night to test with the ronchi screen).now,beleiving this to be a turned up edge(or extreme outer zone) and not wanting to get the center depression deeper i polished with the lap on top, the center of the lap over the edge for five or so minutes, then did center over center for five more, stopped and tested. ronchi lines are straight as can be,and the depression in the center is all but gone.(not the 1/2" radius one in the very center,but it did lessen).i cant beleive i did that, yahoo...one more hurdle crossed,now maybe the edge will polish out.....Thanks for help.