The Full Width at Half Maximum (FWHM) is used as a measure of the optimal size of the aperture ring surrounding the star of interest. Aim is to capture most of the star's light while minimizing contamination from background noise or neighboring stars.


Phoranso incorporates its own FWHM fitting process, modeling star profiles with an anisotropic Moffat function. It uses the Levenberg-Marquardt algorithm to calculate the Moffat function parameters, which then finally are used for the FWHM calculation.