Atmospheric Seeing & Light Pollution: Physical Mechanisms

Seeing depends on turbulence along the line of sight and is often summarized by an angular resolution in arcseconds. Light pollution includes skyglow, glare, light trespass, and clutter, with blue-rich light particularly effective at scattering in the atmosphere.

Turbulent cells with different temperature and density refract incoming wavefronts differently, distorting images on short timescales. Artificial light directed or scattered upward is redirected by molecules and aerosols, adding photons that compete with astronomical signals.

Astronomers measure seeing from stellar image widths and wavefront sensors. Sky-quality meters and calibrated imaging quantify artificial background brightness, while comparisons before and after lighting changes reveal local contributions.

Turbulent cells with changing temperature and density distort the incoming wavefront, causing a star image to wander and spread during an exposure. Artificial photons scattered by aerosols and molecules add background counts that reduce contrast for faint sources. Since signal-to-noise depends on background as well as source brightness, pollution can make a target statistically undetectable even when the telescope collects the same number of source photons.