Hello, Attached are sample fits for time_zero fitting (one good, one bad). Below is a typical summary output for time_zero fitting results for the half stack data: Plane average time_zero and Chi^2 Plane 1 , 3065.36 Chi2 6.75413 Plane 2 , 3065.78 Chi2 8.93485 Plane 3 , 3065.56 Chi2 9.57611 Plane 4 , 3065.70 Chi2 8.28645 Plane 5 , 3066.06 Chi2 8.64475 Plane 6 , 3065.87 Chi2 8.69886 Plane 7 , 3066.30 Chi2 6.84308 Plane 8 , 3065.96 Chi2 6.74808 Plane 9 , 3066.45 Chi2 6.15503 Plane 10 , 3065.90 Chi2 7.38235 Plane 11 , 3066.89 Chi2 5.74342 Plane 12 , 3066.13 Chi2 6.89826 Plane 13 , 0.000000 Chi2 0.000000 Plane 14 , 0.000000 Chi2 0.000000 Plane 15 , 3066.86 Chi2 6.62456 Plane 16 , 3066.56 Chi2 6.46832 Plane 17 , 3067.28 Chi2 5.94262 Plane 18 , 3066.84 Chi2 8.38224 Plane 19 , 3066.70 Chi2 8.23002 Plane 20 , 3066.39 Chi2 7.89158 Plane 21 , 3066.45 Chi2 5.95679 # of rejected fits: 112 out of a possible 1328 Regards, Chris Hynes