In the entry below, at:
we considered the need to remove some residuals left over when a poorly-fitted halo had been removed from the observed image. Sensing that the problem has to do with asymmetry in the solution forced by the lunar disc not being well centred, we consider now the effect of lunar position in the image on the quality of the halo fit. We estimate the quality of the halo fit from the mean value in a sky-patch near the DS.
We see here on the x-axis the value of the disc centre coordinate (i.e. column number in the image) and on the y-axis the mean value of the DS sky patch. We seem to have some scatter as well as a structure that looks like an inverted parabola, for these points near y-value 0. That is – the sky-patch mean value of the DS in images where the halo has been removed with the present EFM method depends on where the lunar disc is – the further away from x0=256 (middle of image) the Moon is, the larger a residual is left on the sky after the halo is removed with the EFM method.
We need to invent a better EFM method!