obscurations

Obscuration is the act or condition of blocking or hiding something from view or access. In scientific and technical contexts, it typically refers to a reduction of transmitted light or information caused by an intervening object or medium. The term covers both complete blocking and partial dimming, and it is often contrasted with related concepts such as occultation, eclipse, and extinction.

In astronomy, obscuration occurs when an opaque body passes in front of a more distant source, producing an occultation or eclipse. Solar eclipses and lunar occultations of stars are common examples, and planetary transits are a form of obscuration where a planet blocks part of a star’s light. Observations of obscuration help determine the sizes, shapes, and atmospheres of celestial bodies. It is important to distinguish obscuration from extinction, which results from diffuse material such as interstellar dust dimming light without a discrete, opaque occluder.

In atmospheric and terrestrial contexts, obscuration refers to reduced visibility caused by aerosols, fog, smoke, dust, or clouds. Such conditions affect ground-based astronomy, aviation, and everyday reporting of visibility. Obscuration can be measured by visibility distance or atmospheric transmission and is influenced by weather, pollution, and seasonal factors.

In optical engineering and instrumentation, obscuration also describes the fraction of an aperture blocked by structural elements or internal components, which can affect light throughput and image quality. Obscuration is a standard consideration in the design of telescopes, cameras, and related imaging systems.

Overall, obscuration is a cross-disciplinary term for any phenomenon that blocks or reduces the passage of light or information through an intervening medium or object.