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
.