A circumscribed halo, often referred to in the context of geology and mineralogy, describes a specific type of alteration zone that surrounds a mineral deposit or a particular rock formation. In this context, the term "halo" indicates a zone around a central feature where certain characteristics, such as mineral composition or chemical properties, change due to processes like hydrothermal alteration or contact metamorphism.

A circumhorizontal arc is a type of optical phenomenon that can be seen in the sky, specifically associated with the refraction of sunlight through ice crystals in cirrus or cirrostratus clouds. It appears as a colorful band of light occurring at the same altitude as the sun but usually appears as a horizontal band or arc that is parallel to the horizon. The circumhorizontal arc is a result of the sunlight passing through ice crystals that have flat, horizontally oriented top surfaces.

Chappuis absorption refers to a phenomenon in atmospheric science, particularly involving the absorption of ultraviolet (UV) radiation by certain atmospheric gases. Specifically, it is most commonly associated with the absorption of UV light by ozone (O₃) in the atmosphere. The term typically describes the specific wavelengths of UV light that ozone absorbs, which is crucial for protecting life on Earth from harmful UV radiation from the sun.

A Brocken spectre is an optical phenomenon that occurs when an observer's shadow is cast upon a cloud or mist while the sun is behind the observer. This results in a magnified and distorted shadow that can appear surrounded by a rainbow-like glory, creating an otherworldly effect. The phenomenon is named after the Brocken, the highest peak in the Harz Mountains of Germany, where it was first observed and described.

The term "Bishop's Ring" can refer to a couple of different contexts, depending on the area of interest. Most notably: 1. **Astronomy**: In the field of astronomy, a "Bishop's Ring" can refer to a ring-like optical phenomenon that can occur around celestial bodies, particularly the Sun or the Moon.

Aurorasaurus is a citizen science project and online platform that allows individuals to report and track auroras, or the Northern and Southern Lights. Launched in 2014, Aurorasaurus aims to gather real-time data on auroral events by collecting reports from amateur astronomers, photographers, and the general public. Users can share their experiences and photographs of auroras, which are then mapped and made available to researchers and the public.

The aureole effect, often referred to in the context of optical phenomena, typically describes a halo-like visual effect where a bright ring or glow appears around a light source. This effect can result from various conditions, including atmospheric conditions, lens imperfections, or certain types of visual representations. In photography and visual arts, the aureole effect can also refer to the way light can create a halo or bright outline around an object.

Atmospheric refraction is the bending of light as it passes through the Earth's atmosphere. This phenomenon occurs because the atmosphere is not a uniform medium; instead, it has varying densities and temperatures, which can change how light travels through it. When light waves enter the atmosphere from space, they encounter layers of air with different properties, primarily due to temperature gradients.

Atmospheric optics is the study of how light interacts with the Earth's atmosphere, leading to various optical phenomena. This field encompasses the understanding of how atmospheric conditions—such as the presence of particles, water vapor, and gases—affect the propagation and perception of light. Some key phenomena studied in atmospheric optics include: 1. **Refraction**: The bending of light rays as they pass through layers of air with different temperatures and densities, leading to phenomena like superior and inferior mirages.

Anticrepuscular rays are a natural phenomenon that occurs when sunlight streams through gaps in clouds or other obstacles, creating beams of light that appear to radiate from a point opposite the sun in the sky, usually near the horizon. This effect is most noticeable during sunrise or sunset when the sun is at a low angle. The term "anticrepuscular" refers to the rays being seen opposite the sun (crepuscular rays appear to extend out from the sun).

An "anthelion" is an atmospheric optical phenomenon that appears as a bright spot in the sky, opposite the sun, typically in the form of a halo. It is part of a family of optical effects caused by the interaction of sunlight with ice crystals in the atmosphere, predominantly occurring in cirrus clouds. The anthelion is located at approximately the same altitude in the sky as the sun, generally at a distance of 22 degrees from it.

Alpenglow refers to the phenomenon where mountains, typically at sunset or sunrise, are bathed in a warm, reddish or pinkish light. This effect occurs when the sun is just below the horizon, casting its rays onto the mountains. The light interacts with the atmosphere and the snow or rocky surfaces of the mountains, creating a beautiful visual display. Alpenglow is often most pronounced on the peaks and ridges, where the sunlight has a more direct angle.

Alexander's band refers to a specific optical phenomenon where a series of dark and bright bands appear around the shadow of an object, typically a planet or a moon, during a solar eclipse or when an object is illuminated in a certain way. The phenomenon is named after the ancient Greek philosopher and scientist Alexander of Aphrodesius, who is often credited with the first recorded observation of this effect.

The Airship of Clonmacnoise refers to a famous report of a sighting of an unidentified flying object (UFO) that allegedly occurred in Clonmacnoise, Ireland, in the mid-20th century. Specifically, the account dates back to the 15th of April, 1989, when multiple witnesses, including a group of school children and their teacher, reported seeing a large, silvery object in the sky.

Airglow is a natural phenomenon characterized by the faint illumination of the night sky caused by the emission of light from atoms and molecules in the Earth's atmosphere.

In astronomy and atmospheric science, "air mass" refers to a measure of the amount of atmosphere that light from a celestial object, such as a star or planet, passes through before it reaches an observer. It is an important concept in understanding the effects of the Earth's atmosphere on astronomical observations. The air mass is typically expressed in terms of a dimensionless quantity that represents the relative thickness of the atmosphere that light traverses.

The term "afterglow" can refer to several concepts depending on the context: 1. **Natural Phenomenon**: In a geographical or astronomical context, afterglow refers to the light that remains in the sky after sunset or twilight. It often creates beautiful colors, typically seen in the sky immediately following sunset.

A 46° halo, also known as a 46-degree halo or 46-degree circular halo, is an optical phenomena that occurs around the sun or moon due to the refraction, reflection, and dispersion of light through ice crystals in the atmosphere. It is characterized by a circular halo that appears at an angular radius of approximately 46 degrees from the sun or moon.

A 22° halo is a type of optical phenomenon that appears as a ring of light encircling the sun or, less commonly, the moon. It is characterized by a radius of approximately 22 degrees from the center of the light source. This phenomenon occurs due to the refraction, reflection, and dispersion of light through ice crystal prisms in the atmosphere, typically found in cirrus or cirrostratus clouds.

The 1561 celestial phenomenon over Nuremberg refers to a mysterious and notable event that occurred on April 14, 1561, in which residents of Nuremberg, Germany, reported seeing a large number of strange objects in the sky. This event was documented in a broadsheet published shortly afterward, which described a "battle" in the sky that involved various shapes and colors, including cylindrical and spherical objects.