Example of the sky emission correction process for an object of the faint subset. Top: slice of the observed 2D raw spectrum with a 3-arcsec slit using OSIRIS in MOS mode. The intensity of the emission from the sky makes it impossible to appreciate the contribution of the observed object. Mid: result obtained by applying the sky subtraction described in the text. This allowed us to recover the emission of the observed object. Bottom: final 1D spectrum obtained for this object. The redshift obtained is z_spec = 0.275 using the observed emission lines.