ImageAnalysis Sketches

Cometary image enhancements

Python implementation of the cometary enhancement filters by N. Samarasinha.

import matplotlib.pyplot as plt
from astropy.io import fits
from sbpy.image import CometaryEnhancement, PSFSubtraction, centroid

im = fits.open('comet.fits')

# cometary enhancement techniques typically need subpixel centering
gyx = 101, 99  # y, x guess
cyx = centroid(im[0].data, gyx, method='comet')  # use the special comet centering method
ayx = centroid(im[0].data, gyz, method='psf')    # use a simple weighted centering model for asteroids 
                                                 # and other point sources

# One class to join them all?
enhance = CometaryEnhancement(im[0], cyx) # MM: added [0] to im, might help to avoid confusion in multi-ext fits

fig, axes = plt.subplots(2, 2)
axes[0, 0].imshow(enhance.azavg_norm())          # divide by azimuthal average, default parameters
axes[0, 1].imshow(enhance.azavg_norm(nth=360))   # use 1 deg steps for x, y to r, th conversion
axes[1, 0].imshow(enhance.rho_norm())            # 1/rho normalization
axes[1, 1].imshow(enhance.rvsf(a=1, b=1, n=0.1)) # radially variable spatial filter

# allow single line enhancements?
axes[1, 0].imshow(CometaryEnhancement.rho_norm(im=im[0].data, yx=cyx))

PSF subtraction tools

Wrappers for PSF subtraction techniques using the photutils affiliated package.

# create a model PSF from all point sources in the field
psfmodel = PSFSubtraction.create_psf(im[0])

# create a model PSF from an activity object
psfmodel = PSFSubtraction.create_psf(im.value, size=20) # with im_value from activity sketches

# subtract psfmodel from source
sub = psfmodel.subtract(im[0], ayx, scaling='peak') # scale psfmodel such that it fits the peak of the target

# create a radial average histogram
from utils import radavg

plt.bar(radavg(sub, ayx))