domenica, ottobre 28, 2007

25 inches mirror on 6 points

Robert Houdart, a member of the BigDob community ( asked me to cross check a benchmark he run with PLOP and a MirrorMesh3D (
I run benchmark 1 in his webpage. It is the case of a 25" 2" thick F/5 mirror supported by 6 points. Here are my raw numbers (before removing defocus): PTV 415 nm, rms 125 nm. Plop says 420 nm and 127 nm respectively, MirrorMesh3D 432 nm and 138 nm.
The pictures show the deformed shape after defocus has been (roughly) removed. I write "roughly" because I did not find the best fitting parabola accurately, but only in the post processing by trial and errors (it is not that difficult).
Picture 1 shows the top view. Picture 2 the view from bottom. Note that support points produce large local deformations that are smoothed on the top side of the mirror.