ISO continuum observations of quasars at z=1-4 -: I.: Spectral energy distributions of quasars from the UV to far-infrared

Eight luminous quasars with -30 < M-B < -27 at z = 1.4-3.7 have been observed in the mid- and far-infrared using ISO. All the quasars have been detected in the mid-infrared bands of ISOCAM, while no far-infrared detections have been made with ISOPHOT. SEDs (Spectral Energy Distributions) from the UV to far-infrared have been obtained while supplementing ISO observations with photometry in the optical and near-infrared made from the ground within 17 months. The SEDs are compared with the MED (Mean spectral Energy Distributions) of low-redshift-quasars with -27 < MB < -22. It is shown. that our far-infrared observations were limited by confusion noise due to crowded sources.