The observations described in Section IV.A.4 established that flux densities greater than 10 Jy at 60 and 100 um are in error of at least 30% at 60 µm and up to 70% at 100 µm because the responsivity of the detectors varied with the total flux on the detectors. This effect depends on the background as well as
XI-1
on the brightness of the source itself. The photometry of any source in a background greater than 10 MJy sr-1 at 60 and 100 µm is therefore suspect.