On the ground

As we saw, photometry on the ground for our supernovæ imply two in general, three to see four different telescopes, each one of these instruments having different characteristics. In particular, vary, the size of the pixels, the atmospheric conditions (in particular the seeing) or field of observation cuts it. Figure 8.1 illustrates, with the images of the same supernova for three different instruments, the influence of the seeing on the quality of the observations.

It is thus essential if one wants to be able to make a comparison of the images of follow-up to the images of major reference homogenize the images in the same conditions.

Figure 8.1: Illustration of the variations of seeing from one instrument to another. This image shows the supernova 1997eq towards its maximum of luminosity. The three images top are taken at one day of variation with respectively camera WFPC2 of the space telescope Hubble, the WIYN and the INT, the size of the fields are the same one for the three images. In bottom, the distribution in two dimensions of the pixels centered on the supernova for each image is represented.