Obscuration

Obscuration is the act or condition of obscuring; the process by which something becomes hidden, unclear, or blocked from view or detection. It can refer to physical blocking of light or sound, or to the metaphorical obscuring of information. The term derives from Latin obscurare, to darken.

In scientific usage, obscuration covers phenomena that reduce visibility or signal strength, such as dust, clouds, fog, smoke, or opaque objects, and can be temporary or permanent. It can arise from natural or artificial obstructions and may affect perception, measurement, or communication.

In astronomy, obscuration describes the reduction of a background source's brightness by intervening material or bodies. It can be complete (occultation) or partial (extinction and scattering). Obscuration by interstellar dust causes extinction and reddening; by planetary atmospheres or moons for solar and lunar occultations and transits; and by circumstellar or interstellar gas. Obscuration influences the interpretation of astronomical observations and often requires corrections across wavelengths.

In Earth's atmosphere and on the surface, obscuration affects visibility and the quality of measurements from ground-based instruments. Clouds, fog, haze, smoke, and terrain can obscure signals in optical, infrared, and radio observations. In remote sensing, obscuration reduces radiance and resolution; in optics, central obscuration can result from telescope design, reducing throughput.

Quantifying obscuration typically uses transmission (T), optical depth (tau), or extinction measures. Observers may report the obscured fraction or the degree of attenuation. Mitigation strategies include observing at longer wavelengths less affected by dust, using adaptive optics or space-based instruments, and applying algorithms to correct for extinction or to reconstruct obscured information.

See also: occultation, extinction, cloud cover, atmospheric transparency.