Relation between the quantity of sampled stars and the ePSF mode's accuracy in Astrometry

摘要

Effective point-spread function(ePSF) method is an excellent method for the positional measurements of stars in undersampled stellar images, whose critical step is deriving an accurate ePSF mode. In the presentation, we investigate the effects of the grid density and the sample density on the mode's accuracy through some experiments on positional measurement in synthetic undersampled stellar images. We find that constructing a stable ePSF mode requires two samples in every cell (basic unit of pixel segmentation) for a certain grid. That is, ideally, 2n2 sampled stars in a stellar image are enough for constructing a stable ePSF mode. Whether the derived stable ePSF mode is accurate is related to the grid density, the denser the mode's grid is, the more accurate it is.