Top row: de-reddened i₀ vs. g − i₀ Hess diagrams of the shell (left) and control field 1 (ConF1, right). The solid lines are BaSTI isochrones with ages of 30, 150, 800 Myr, 2.5, 6, and 13.5 Gyr shifted assuming a distance modulus of 18.96 mag. The metallicity of the oldest isochrone is Z = 0.001 dex, whereas we have adopted a metallicity of Z = 0.002 dex for the younger isochrones (see text). Bottom left: i₀ vs. g − i₀ synthetic CMD computed using the BaSTI stellar population synthetic program web tool for a constant SFH from 13.5 Gyr to 30 Myr ago. The solid lines are the same isochrones as shown in the top row. The horizontal dashed line corresponds to our absolute magnitude cut of M_i = 3 mag for deriving the color function (see text). Bottom right: i₀ luminosity functions of the shell, ConF1, and the synthetic CMD. The horizontal dashed line again corresponds to M_i = 3 mag and demonstrates that at fainter magnitudes completeness starts to become an issue for the shell and ConF1 CMDs.