The CellaCrystal PA 64 has been developed for optical temperature measurement during the growth of crystals with the plasma-assisted CVD process. Thanks to the quotient measurement method and the special wavelength, the measurement is minimally influenced by the plasma. Combined with the constant high resolution of < 0.1 K over the entire measuring range and the very high long-term stability, the device meets the requirements for the necessary high measurement accuracy. With the help of the through-the-lens sighting, laser pilot light or video camera, the pyrometer can be precisely aligned to the measuring point.