This is a time-lapse video showing Crepuscular Rays. These are shafts of light that appear to radiate from the sun. The effect is caused by the sunlight scattering from aerosols, i.e. small particles such as dust and smoke that are suspended in the atmosphere. It is usually seen when broken clouds are present, which leads to alternating shafts of light and shadow. The rays of light from the sun are actually parallel, but they appear to converge because of the effects of perspective. This is the same effect that makes roads appear to become more narrow as they recede into the distance. The word crepuscular implies twilight and so the term crepuscular rays is sometimes reserved for the effect that is seen when the sun is just below the horizon. However, crepuscular rays can potentially be seen at any time of day. They tend to be most dramatic when the sun is low in the sky and when the concentration of aerosols is particularly high. Although the clouds in this video look like Cumulus, the cloud base (detected by a laser ceilometer at the same location as the camera) is above 2 km suggesting that they are Altocumulus castellanus. This video has been created from images taken by the Sky-Camera at the National Centre for Atmospheric Science (NCAS) Capel Dewi Atmospheric Observatory (CDAO) near Aberystwyth, UK - formerly known as the Natural Environment Research Council (NERC) Mesosphere-Stratosphere-Troposphere (MST) Radar Facility. The images are freely available under a UK Open Government Licence from http://tinyurl.com/nerc-mstrf-sky-camera/ . For more details visit https://amof.ac.uk/instruments/cdao-sky-camera/ .