EPSFBuilder¶
- class photutils.psf.EPSFBuilder(*, oversampling=4, 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, recentering_boxsize=(5, 5), center_accuracy=0.001, sigma_clip=SigmaClip(sigma=3, sigma_lower=3, sigma_upper=3, maxiters=10, cenfunc='median', stdfunc='std', grow=False))[source]¶
Bases:
object
Class to build an effective PSF (ePSF).
See Anderson and King (2000; PASP 112, 1360) and Anderson (2016; WFC3 ISR 2016-12) for details.
- Parameters:
- oversamplingint or array_like (int)
The integer oversampling factor(s) of the ePSF relative to the input
stars
along each axis. Ifoversampling
is a scalar then it will be used for both axes. Ifoversampling
has two elements, they must be in(y, x)
order.- 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 well-defined 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 custom fitter options, input a newEPSFFitter
object. See theEPSFFitter
documentation for options.- maxitersint, optional
The maximum number of iterations to perform.
- progress_barbool, option
Whether to print the progress bar during the build iterations. The progress bar requires that the tqdm optional dependency be installed. Note that the progress bar does not currently work in the Jupyter console due to limitations in
tqdm
.- norm_radiusfloat, optional
The pixel radius over which the ePSF is normalized.
- 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 must be in
(ny, nx)
order.recentering_boxsize
must have odd must have odd values and be greater than or equal to 3 for both axes.- 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.- sigma_clip
astropy.stats.SigmaClip
instance, optional A
SigmaClip
object that defines the sigma clipping parameters used to determine which pixels are ignored when stacking the ePSF residuals in each iteration step. IfNone
then no sigma clipping will be performed.
Notes
If your image image contains NaN values, you may see better performance if you have the bottleneck package installed.
Methods Summary
__call__
(stars)Call self as a function.
build_epsf
(stars, *[, init_epsf])Build iteratively an ePSF from star cutouts.
Methods Documentation