  Aiming to extract cosmological information from linear scales of the
WISE$\times$SuperCOSMOS photometric redshift catalog, we perform a
characterization of the systematic effects associated with stellar content,
evidencing the presence of contamination and obscuration. We create an
integrated model for these effects (which together we call `usurper
contamination'), devise a method to remove both of them simultaneously and show
its functionality by applying it to a set of mock catalogs. When administered
to WISE$\times$SuperCOSMOS data, our method shows to improve the measurements
of angular power spectra on scales $\ell\lesssim15$ and the extraction of
cosmological parameters therefrom, even though a significant excess of power
remains at these scales. When ignoring scales $\ell<15$, we still find strong
indications of systematics, albeit these can be localized in the southern
equatorial hemisphere. An independent analysis of the northern hemisphere at
$\ell\geq 15$ agrees with a $\Lambda$CDM model with parameters from the Planck
satellite and gives $\Omega_{\mathrm{c}}=0.254\pm0.020$ and
$\Omega_{\mathrm{b}}<0.065$ at 95% confidence limit when combined with priors
on $H_0$, $A_s$ and $n_s$.
