Light pollution
Light pollution is the level of radiance (night lights) shining up into the night sky. The Campaign to Protect Rural England (CPRE) divides the level of night sky brightness into 9 bands with band 1 being the darkest i.e. with the lowest level of light pollution and band 9 the brightest and most polluted. Broom with an index of 1-2 nanoWatts (nW) is in band 4. The night sky brightens towards Biggleswade but is darker to the west.