mirror cell design

It turns out that a lot of work has been done comparing the "equal area/weight" method for mirror cell design to more complex methods based on finite element analysis. In particular a program PLOP has been developed by David Lewis, and some results are given here. In general, the results reassure me that the 37.6% and 80.5% radii, which are from Kriege & Barry and which I used for my 16" scope, are within the range of values arrived at by various combinations of mirror thickness and secondary obstruction parameters. The chief difference is that their radii are skewed outwards a little bit by the assumption that flexion of the obscured central portion of the mirror can be disregarded; however, the difference is not large. Plus, they suggest that 9 points would suffice for a 16" mirror, so my 18 point cell be over-engineered anyway. Phew!