A thermographic weapon sight, thermal imagery scope or thermal weapon sight is a device combining a compact thermographic camera and an aiming reticle. They can be mounted on a variety of small arms as well as some heavier weapons. As with regular thermal sensors, thermal weapon sights can operate in total darkness or through light concealment (smoke, haze, fog, light rain). The thermal scope can be quite useful in places with snow as the large contrast in temperatures between the snow (inherently cold) and any heat source (such as humans) make it very easy to distinguish between the two.