`CAL_omGetPSF`- controls the pointers for the next routines
`CAL_omPsfEncircledEnergy`- computes the fraction of the energy contained in a circle of a given radius centered on the PSF centroid
`CAL_omPsfCircleRadius`- computes the radius of a circle centered on the PSF barycentre containing a given fraction of the total energy

Michael Smith 2011-09-20