Zemax has been busy and it will stay busy this week. I was reassured that it should be free next week. I only managed to get few spots out of Zemax a It is not obvious to me that the conclusions from optical telescopes apply here. I plan to finish this analysis with more spots so that we can clearly see what is happening next week.

As Seen in the attached Figures, it does seem that hypothesis stated in the description of the task is correct. We are looking if we can use this knowledge in further work. In any case, the conclusion of the discussion with R. Lupton and J. Gunn on April 3 is that the way that I was doing until now (fitting 2nd order polynomial in x- and y- direction) is insufficient. We believe that z4, z11, z22 shapes are due to the tilting of the detector. Also we might expect some extra effects due to grating (mainly trefoil).