A review on far-infrared brightness-temperature maps of the solar atmosphere is presented. They have been taken with the aid of a 60 cm-diameter balloon-borne telescope at a height of 39 km in France. Three bandpass filters at the wavelengths 50 μm, 80 μm and 200 μm of 6 to 10 % bandwidth have been applied. The filters as well as the Au-doped Ge bolometer were cooled by liquid He. An
observation on 30.4.83 represents the active sun, while one on 28.9.84 shows the quiet sun. The observations at the three wavelengths correspond to three different heights in the solar atmosphere at the transition of the photosphere and chromosphere. Over active regions, average temperature enhancements of 75 K to 250 K are observed relative to the inactive regions depending of the height in the solar atmosphere.