In white light this lens shows very good smoothness and around 1/8 wavefront p.t.v.. Using a green filter, the lens show even smoother and could be estimated at 1/10 wavefront p.t.v. or even better, to good to give an real estimation. I think the strehl is in any case in the 99% area or better.
Markus Ludes (APM-Telescopes)
Note: ronchi-testing with 254 lines/inch or 100 lines/cm.