Thursday

The sky in the Malvern Hills Area of Outstanding Natural Beauty (MHAONB) has been monitored continually since 2012, when a dark sky survey of the area was carried out commissioned by Malvern Hills Conservators. Ever since then at Mathon observatory, the sky brightness has been measured continually, in the last few years at minute intervals in all weathers. On the darkest of nights, a fisheye lensed camera was used at the same intervals. There is a trend in brightness distribution and colour changes on the sky towards the horizon, with well separated bright sky domes. The sky quality meter (SQM) photometry data near zenith does not show any great change. In 2015, Malvern Hills Conservators commissioned the author for modelling of the effect on the MHAONB sky, of the ongoing blue rich LED re-lighting throughout Herefordshire.
The camera shows the near horizon colour trend from orange-pink to blue-rich LEDs over the years. The SQM photometry shows the sky brightness distribution is very weather dependent. Colour and brightness changes can also occur over hours or even minutes, depending on cloud cover over individual towns on or beyond the horizon. In poor visibility the sky is darker and more dominated by local sources, while over horizon one attenuated. Clear sky brightness always falls overnight, most likely the fall in temperature resulting in humidity reaching dew point. The major advances since previous papers are the following:
• The database now includes 2020 with a study of light pollution changes during Covid-19 complete lockdown. In this rural area, only the normal weather variation was found.
• From samples of the all sky images, isophotes were plotted with identifiable city sky domes up to 120 km away. Images show significant differences of sky dome distributions from satellite data base simulations for