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Issue #4
Affects EDR, DR1

Spatially varying PSF affecting photometry

Issue raised May 02 2016, 02:20; last modified Jun 05 2017, 05:55

Photometry is affected by a spatially varying PSF across the field-of-view, and the PSF shows trefoil in the corners and generally significant floors. Current aperture photometry includes a pixel-position-dependent aperture correction derived from bright stars and suppresses the propagation of PSF variation for point sources. PSF photometry is currently not a 2D-PSF-fit, but a 1D-fit to the sequence of aperture-corrected measurements in a sequence of apertures. Kron and Petrosian photometry is taken unchanged from Source Extractor.

Future data releases will include a PSF magnitude derived by fitting the actual PSF.