$\star$ Estimate of fluxes

We can now apply the equation 8.4 which will give us optimal flux.

One can wonder how this approach `` split '' (position, then flux) is compared with a simultaneous estimate of these parameters, for example by the maximum of probability, which would be reduced here to least squares. In fact, the resolution of the normal equations of the adjustment of total PSF (position and flux simultaneously) by the method of Gauss-Newton is reduced primarily to two filterings which we described.