The CellaCrystal PX 44 has been developed for optical temperature measurement during the growth of silicon crystals. The calibration is specially adapted to the production of crystals. Combined with the constantly high resolution of < 0.1 K over the entire measuring range and the very high long-term stability, the instrument meets the requirements in terms of accuracy and stability. The pyrometer can be precisely aligned to the measuring point with the aid of the through-the-lens sighting, laser pilot light or video camera.