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A Bottlinger's ring is a rare type of halo that is elliptical instead of circular. It has a small diameter, which makes it very difficult to see in the Sun's glare and more likely to be noticed around the dimmer subsun, often seen from mountain tops or airplanes. Bottlinger's rings are not well understood yet.
22° halo around the Sun 22° halo around the Moon. A 22° halo is an atmospheric optical phenomenon that consists of a halo with an apparent diameter of approximately 22° around the Sun or Moon. Around the Sun, it may also be called a sun halo. [1] Around the Moon, it is also known as a moon ring, storm ring, or winter halo.
The corotation circle is the circle around the galactic center of a spiral galaxy, where the stars move at the same speed as the spiral arms. The radius of this circle is called the corotation radius. Inside the circle the stars move faster and outside they move slower than the spiral arms. The Sun is located near the corotation circle of the ...
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.
Equal chords are subtended by equal angles from the center of the circle. A chord that passes through the center of a circle is called a diameter and is the longest chord of that specific circle. If the line extensions (secant lines) of chords AB and CD intersect at a point P, then their lengths satisfy AP·PB = CP·PD (power of a point theorem).
Circumpolar star trails in a long-exposure photo of several hours. The stars near the celestial pole leave shorter trails with the long exposure. A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles.
Over the course of an evening in the Northern Hemisphere, circumpolar stars appear to circle around the north celestial pole. Polaris (within 1° of the pole) is the nearly stationary bright star just to the right of center in this star trail photo.
A chord of a circle is a line segment whose endpoints are on the circle. Ptolemy used a circle whose diameter is 120 parts. Ptolemy used a circle whose diameter is 120 parts. He tabulated the length of a chord whose endpoints are separated by an arc of n degrees, for n ranging from 1 / 2 to 180 by increments of 1 / 2 .