skyglow 
noun [mass noun]
Brightness of the night sky in a built-up area as a result of light pollution: at night the stars and planets are obliterated by glare and skyglow...
- Light pollution occurs when too much artificial illumination enters the night sky and reflects off airborne water droplets and dust particles causing ‘skyglow’.
- A combination of skyglow, clouds, and insufficient aperture kept me from spotting it, though the sites farther east were much darker.
- It's the skyglow, from artificial lights and smog.