Question about aperture size

[temuller]

Hi, I am trying to understand something about the size aperture used for aperture photometry. I extract the objects in my image with sep.extract() and then estimate the kron radius with:

kronrad, krflag = sep.kron_radius(data_sub, objects['x'], objects['y'], 
                                  objects['a'], objects['b'], objects['theta'], 6.0)

To estimate the aperture flux, I use:

flux, fluxerr, flag = sep.sum_ellipse(data_sub, objects['x'], objects['y'], 
                                      objects['a'], objects['b'], objects['theta'], 2.5*kronrad,
                                      subpix=1, gain=1.0)

Where the 2.5 is the usual scale of the kron radius, I believe. If I understand this correctly, the actual ellipse size used for the aperture flux would have parameters 2.5*kronrad*objects['a'] and 2.5*kronrad*objects['b'], right? So, if I want to plot the actual ellipse size used I would need to use the following:

fig, ax = plt.subplots(figsize=(8, 8))
ax.imshow(data_sub, interpolation='nearest', cmap='gray',
               vmin=m-s, vmax=m+s, origin='lower')

# plot an ellipse for each object
for i in range(len(objects)):
    e = Ellipse(xy=(objects['x'][i], objects['y'][i]),
                width=2.5*kronrad*objects['a'][i],
                height=2.5*kronrad*objects['b'][i],
                angle=objects['theta'][i] * 180. / np.pi)
    e.set_facecolor('none')
    e.set_edgecolor('red')
    ax.add_artist(e)
plt.show()

I basically want to know if the aperture size used to calculate the flux of a galaxy actually surrounds the entire galaxy.