Once the candidates identified like supernova of the type Ia, one selects most interesting (early phase of the lightcurve, great redshift) to follow them with observation aids more adapted. The most remote supernovæ will be observed with the space telescope Hubble, closest, with telescopes of 4m with small field during their phase around the maximum, then by telescopes of 8m for the late phases.
Most remote (with redshifts beyond 1) will be also followed in the infra-red (in the band J mainly). This follow-up makes it possible to make photometry in the bands B or V in the reference frame of the supernova and thus allows measurements of color in order to estimate a possible absorption.