EPSFBuilder¶

class
photutils.psf.
EPSFBuilder
(oversampling=4.0, shape=None, smoothing_kernel='quartic', recentering_func=<function centroid_com>, recentering_maxiters=20, fitter=<photutils.psf.epsf.EPSFFitter object>, maxiters=10, progress_bar=True, norm_radius=5.5, shift_val=0.5, recentering_boxsize=(5, 5), center_accuracy=0.001, flux_residual_sigclip=SigmaClip(sigma=3, sigma_lower=3, sigma_upper=3, maxiters=10, cenfunc=<function nanmedian>, stdfunc=<function nanstd>, grow=False))[source]¶ Bases:
object
Class to build an effective PSF (ePSF).
See Anderson and King (2000; PASP 112, 1360) and Anderson (2016), ISR WFC3 201612 for details.
 Parameters
 oversamplingint or tuple of two int, optional
The oversampling factor(s) of the ePSF relative to the input
stars
along the x and y axes. Theoversampling
can either be a single float or a tuple of two floats of the form(x_oversamp, y_oversamp)
. Ifoversampling
is a scalar then the oversampling will be the same for both the x and y axes. shapefloat, tuple of two floats, or
None
, optional The shape of the output ePSF. If the
shape
is notNone
, it will be derived from the sizes of the inputstars
and the ePSF oversampling factor. If the size is even along any axis, it will be made odd by adding one. The output ePSF will always have odd sizes along both axes to ensure a welldefined central pixel. smoothing_kernel{‘quartic’, ‘quadratic’}, 2D
ndarray
, orNone
The smoothing kernel to apply to the ePSF. The predefined
'quartic'
and'quadratic'
kernels are derived from fourth and second degree polynomials, respectively. Alternatively, a custom 2D array can be input. IfNone
then no smoothing will be performed. recentering_funccallable, optional
A callable object (e.g., function or class) that is used to calculate the centroid of a 2D array. The callable must accept a 2D
ndarray
, have amask
keyword and optionallyerror
andoversampling
keywords. The callable object must return a tuple of two 1Dndarray
variables, representing the x and y centroids. recentering_maxitersint, optional
The maximum number of recentering iterations to perform during each ePSF build iteration.
 fitter
EPSFFitter
object, optional A
EPSFFitter
object use to fit the ePSF to stars. To set fitter options, a new object with specific options should be passed in  the default uses simply the default options. To see more of these options, see theEPSFFitter
documentation. maxitersint, optional
The maximum number of iterations to perform.
 progress_barbool, option
Whether to print the progress bar during the build iterations.
 norm_radiusfloat, optional
The pixel radius over which the ePSF is normalized.
 shift_valfloat, optional
The undersampled value at which to compute the shifts. It must be a strictly positive number.
 recentering_boxsizefloat or tuple of two floats, optional
The size (in pixels) of the box used to calculate the centroid of the ePSF during each build iteration. If a single integer number is provided, then a square box will be used. If two values are provided, then they should be in
(ny, nx)
order. center_accuracyfloat, optional
The desired accuracy for the centers of stars. The building iterations will stop if the centers of all the stars change by less than
center_accuracy
pixels between iterations. All stars must meet this condition for the loop to exit. flux_residual_sigclip
SigmaClip
object, optional A
SigmaClip
object used to determine which pixels are ignored based on the star sampling flux residuals, when computing the average residual of ePSF grid points in each iteration step.
Methods Summary
__call__
(stars)Call self as a function.
build_epsf
(stars[, init_epsf])Iteratively build an ePSF from star cutouts.
Methods Documentation