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PSF-Kron

The simplest way is to use the difference between PSFMag and KronMag. This has the advantage that it is available for all objects in the survey.

Image Added

This example is from a stack sample around Abell1656

matched to SDSS and coloured by SDSS classification

(red - stars; black - galaxies). A cut in iPSFMag-iKronMag of

0.05 (shown) does a reasonable job of separating stars and

galaxies.

You can calculate this using data from the MeanObject, StackObjectThin or ForcedMeanObject tables. You might improve the separation by combining results from more than one band.

Below i ~21 this simple cut becomes unreliable (usually over-predicts the number of stars). Also be aware that once stars become saturated (brighter than i ~14 in this example) they shift to the galaxy side of the cut.