An automatic precise polychromatic pyrometer

The pyrometer is described here, which has a slight smaller precision than large scale experimental arrangements can be transported, as well as being polychromatic. The last mentioned property means that it can be used to measure source brightness temperatures at six wavelengths between 430 and 690 nm. In this way the energy distribution of a source, in absolute units can be quickly obtained. The instrument was calibrated at the melting point of gold with a black body of the Institut d'astrophysique de Paris and is regularly checked. The temperature scale was set up to about 2500 K at the six wavelengths. The precision varies between 0.3 and 1 K depending on the wavelength and the temperature.