Summary: Issues related to the geometric and photometric calibration of the Astro Line Spread Function (LSF) are briefly discussed, in particular the separation of shape, position and flux, and the precise definition of the centroid. A convention for the centroid definition is proposed, based on a simple analytical weighting function, which appears close to optimal (for Gaia-3 parameters and typical WFE) from the viewpoint of statistical precision and interpolation accuracy. It is furthermore proposed that this weighting function is used for the very initial centroiding on AF samples, before the LSF has been calibrated.


Bibtex entry for this abstract:

author = {L.~Lindegren},
title={{C}entroid definition for the {A}stro {L}ine {S}pread {F}unction},
institution={Lund Observatory},
type={Technical note}