Data Reduction
Astronomical aspherical mirrors may be analysed with a Foucault test, called often Knife-Edge test. The test may be
considered, in general, as a method for determining the presence of transverse aberration. This is done by blocking
out one part of a plane traversed by rays so that a shadow appears over the aberrated region. This high simplicity
of operation and interpretation makes the Foucault test unique among optical testing methods. Finally measured data
can be graphical represent.