  Theoretical studies of the physical processes in clusters of galaxies are
mainly based on the results of numerical simulations, which in turn are often
directly compared to X-ray observations. Although trivial in principle, these
comparisons are not always simple. We show that the projected spectroscopic
temperature of clusters obtained from X-ray observations is always lower than
the emission-weighed temperature. This bias is related to the fact that the
emission-weighted temperature does not reflect the actual spectral properties
of the observed source. This has implications for the study of thermal
structures in clusters, especially when strong temperature gradients, like
shock fronts, are present. In real observations shock fronts appear much weaker
than what is predicted by emission-weighted temperature maps.
  We propose a new formula, the spectroscopic-like temperature function that
better approximates the spectroscopic temperature, making simulations more
directly comparable to observations
