PSF Fitting

A few PSF fitting utilities are included to interface between observations within Roman datamodels and methods within dependencies that generate and fit PSF models to observations.

Create PSF models

create_gridded_psf_model computes a gridded PSF model for a given detector using CreatePSFLibrary from WebbPSF. The defaults are chosen to balance more accurate PSF models with the cost of increased runtime. For further reading on the WebbPSF approach to ePSFs, see the WebbPSF docs on Using PSF Grids.

Fit model PSFs to an ImageModel

Once PSF models are generated, you can fit those models to observations in an ImageModel with fit_psf_to_image_model using photutils. By default the fits are done with PSFPhotometry, and crowded fields may benefit from using IterativePSFPhotometry. For neighboring sources that are near one another on the detector, grouping the sources and fitting their PSFs simultaneously improves the fit quality. Initial guesses for target centroids can be given or source detection can be performed with, e.g., DAOStarFinder.