A compact furnace for calibrating radiation pyrometers, the Pegasus R sets the temperature of the furnace on a controller while an independent indicator, whose sensor is built into the furnace’s cavity, indicates the actual radiance temperature. The cavity’s diameter is 20mm (0.8”). The depth is 65mm (2.6”). The emissivity is 0.995. The cavity is removable and a fixed-point cell may be put in its place.