The Pegasus R is a compact furnace for calibrating radiation pyrometers. The temperature of the furnace is set on a controller, whilst an independent indicator, whose sensor fits into the cavity, indicates the actual radiance temperature. The sensor can be removed for external calibration or the complete system can be calibrated. The cavity diameter is 20mm, the depth 65mm. Emissivity is 0.995. The cavity is removable and a fixed point cell may be put in its place. The cavity inside the fixed point cell is 10mm in diameter by 65mm deep to the tip of a 120° cone. Blackbody target radiation source for use with Pegasus R. For calibration radiation thermometers in the wavelength range 0.9 to 14 micrometres. A blackbody radiation source ‘based on a design study by England’s National Physical Laboratory (NPL)’ for Isothermal Technology Ltd is housed, with suitable insulation, in the Pegasus tube furnace. The aperture is 20mm in diameter. A Pegasus blackbody source has been calibrated at NPL (Nat. Physical Laboratory) with an uncertainty of ±2°C and the calibration was found to be reproducible after a period of about 2 months. A scan across the aperture at 444°C showed that the source was uniform to better than 0.3°C. Traceability may be established with a UKAS certificate for the in-built indicator and supplied probe (935-14-40).