Optics Module usage

The GalSim optics module is a collection of simple Python commands for generating images of simple, generic PSFs such as come from Telescope optics, modelled with low order aberrations.

Input aberration coefficients are assumed to be supplied in units of wavelength, and correspond to the definitions given here: http://en.wikipedia.org/wiki/Optical_aberration#Zernike_model_of_aberrations