Image of the distorted disc of the full Moon. In this position the moonlight must pass through an increasing mass of air and the distortions caused by the refraction of light become significant. Such distortions reflect the presence of masses of air with different densities and temperatures and consequently refractivities. Another effect visible here is the reddening of the moonlight. This is caused by particulate matter such as dust and aerosols suspended in the atmosphere. These particles scatter blue light more strongly than red light making the lunar disc redder and the rest of the sky blue.