Quickstart Guide

spike is intended to be simple to use. At minimum, one just needs a working directory and object coordinates to begin. The working directory should be structured to include calibrated, but not yet combined .fits files from a single instrument on a single telescope. For example:

from spike import psf

acs_path = '/path/to/acs/data/'

### TinyTim ###
psf.hst(img_dir = acs_path, obj = '10:00:33.0178 +02:09:52.304', img_type = 'flc',
        inst = 'ACS', camera = 'WFC', method='TinyTim', savedir = 'psfs_tiny', verbose = True,
        pretweaked = False)

### TinyTim (Gillis et al. mod) ###
psf.hst(img_dir = acs_path, obj = '10:00:33.0178 +02:09:52.304', img_type = 'flc',
        inst = 'ACS', camera = 'WFC', method='TinyTim_Gillis', savedir = 'psfs_tinygillis',
        verbose = True, pretweaked = True)

### STDPSF ###
psf.hst(img_dir = acs_path, obj = '10:00:33.0178 +02:09:52.304', img_type = 'flc',
        inst = 'ACS', camera = 'WFC', method='stdpsf', savedir = 'psfs_stdpsf', verbose = True,
        pretweaked = True)

### ePSF ###
psf.hst(img_dir = acs_path, obj = '10:00:33.0178 +02:09:52.304', img_type = 'flc',
        inst = 'ACS', camera = 'WFC', method='epsf', savedir = 'psfs_epsf', verbose = True,
        pretweaked = True)

### PSFEx ###
psf.hst(img_dir = acs_path, obj = '10:00:33.0178 +02:09:52.304', img_type = 'flc',
        inst = 'ACS', camera = 'WFC', method='PSFEx', savedir = 'psfs_psfex', verbose = True,
        pretweaked = True)

In lieu of passing coordinates to obj, you can also provide an object name (as long as it’s resolvable by NED/Simbad). For example:

from spike import psf

acs_path = '/path/to/acs/data/'

psf.hst(img_dir = acs_path, obj = 'M79', img_type = 'flc', inst = 'ACS', camera = 'WFC')


nircam_path = '/path/to/nircam/data/'

psf.jwst(img_dir = nircam_path, obj = 'M79', img_type = 'cal', inst = 'NIRCam')

The last code block shows minimal examples, which include all of the required inputs (camera is only required for ACS and WFC3). spike handles filter and detector/chip identification automatically, and the default parameters are sufficient to produce PSFs in most cases. The top-level functions spike.psf.hst, spike.psf.jwst, and spike.psf.roman also take a number of keyword arguments that allow for near-complete customization of the generated PSFs.

Note that it will often be preferred to provide a savedir argument, as otherwise files with the same name may be overwritten in the default /psfs directory.

The output drizzled/resampled PSF is placed in the full spatial context of the processed frames by default. A convenience function is included to crop the data to the region immediately around the PSF, spike.tools.cutout. Alternatively, setting returnpsf = ‘crop’ in the spike.psf functions will result in a cutout around the PSF coordinates with a size set by the cutout_fov argument.

spike.tools and spike.psfgen functions can also be used in isolation.