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The three interior angles of the celestial triangle. The figure to the right represents the three angular distances. The left one represents the angle at the observed pointing between the zenith direction and the solar direction. This is thus heavily dependent on the changing solar direction as the Sun is perceived as moving across the sky.
The circumzenithal arc, also called the circumzenith arc (CZA), the upside-down rainbow, and the Bravais arc, [1] is an optical phenomenon similar in appearance to a rainbow, but belonging to the family of halos arising from refraction of sunlight through ice crystals, generally in cirrus or cirrostratus clouds, rather than from raindrops.
The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), [1] [2] is the area of the sky that is obscured by the Milky Way. [ 3 ] The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard Proctor that referred to the distribution of " nebulae " in John Herschel 's General ...
Angular diameter: the angle subtended by an object. The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is the angular aperture (of ...
Other colours in the sky, such as glowing skies at dusk and dawn. These are from additional particulate matter in the sky that scatter different colors at different angles. Halos, afterglows, coronas, polar stratospheric clouds, and sun dogs. These are from scattering, or refraction, by ice crystals and from other particles in the atmosphere ...
A water glass experiment (known about since at least 1920) may be modified slightly to create an artificial circumhorizontal arc. Illuminating under a very steep angle from below the side face of a nearly completely water-filled cylindrical glass will refract the light into the water. The glass should be situated at the edge of a table.
The navigational triangle or PZX triangle is a spherical triangle used in astronavigation to determine the observer's position on the globe. [1] It is composed of three reference points on the celestial sphere: P is the Celestial Pole (either North or South). It is a fixed point. Z is the observer's zenith, or their position on the celestial ...
Right ascension and declination as seen on the inside of the celestial sphere. The primary direction of the system is the March equinox, the ascending node of the ecliptic (red) on the celestial equator (blue). Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction.