Antisolar point in the context of "Gegenschein"

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⭐ Core Definition: Antisolar point

The antisolar point is the abstract point on the celestial sphere directly opposite the Sun from an observer's perspective. This means that the antisolar point lies above the horizon when the Sun is below it, and vice versa. On a sunny day, the antisolar point can be easily found; it is located within the shadow of the observer's head. Like the zenith and nadir, the antisolar point is not fixed in three-dimensional space, but is defined relative to the observer. Each observer has an antisolar point that moves as the observer changes position.

The antisolar point forms the geometric center of several optical phenomena, including subhorizon haloes, rainbows, glories, the Brocken spectre, and heiligenschein. Occasionally, around sunset or sunrise, anticrepuscular rays appear to converge toward the antisolar point near the horizon. However, this is an optical illusion caused by perspective; in reality, the "rays" (i.e. bands of shadow) run near-parallel to each other.

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👉 Antisolar point in the context of Gegenschein

Gegenschein (/ˈɡɡənˌʃn/; German: [ˈɡeːɡn̩ˌʃaɪn]; lit.'counter-shine') or counterglow is a faintly bright spot in the night sky centered at the antisolar point. The backscatter of sunlight by interplanetary dust causes this optical phenomenon, being a zodiacal light and part of its zodiacal light band.

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Antisolar point in the context of Rainbows

A rainbow is an optical phenomenon caused by refraction, internal reflection and dispersion of light in water droplets resulting in a continuous spectrum of light appearing in the sky. The rainbow takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. Rainbows can be caused by many forms of airborne water. These include not only rain, but also mist, spray, and airborne dew.

Rainbows can be full circles. However, the observer typically sees only an arc formed by illuminated droplets above the ground, and centred on a line from the Sun to the observer's eye.

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Antisolar point in the context of Zodiacal light

The zodiacal light (also called false dawn when seen before sunrise) is a faint glow of diffuse sunlight scattered by interplanetary dust. Brighter around the Sun, it appears in a particularly dark night sky to extend from the Sun's direction in a roughly triangular shape along the zodiac, and appears with less intensity and visibility along the whole ecliptic as the zodiacal band. Zodiacal light spans the entire sky and contributes to the natural light of a clear and moonless night sky. A related phenomenon is gegenschein (or counterglow), sunlight backscattered from the interplanetary dust, which appears directly opposite to the Sun as a faint but slightly brighter oval glow.

Zodiacal light contributes to the natural light of the sky, though since zodiacal light is very faint, it is often outshone and rendered invisible by moonlight or light pollution.

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Antisolar point in the context of Midnight

Midnight is the transition time from one day to the next – the moment when the date changes, on the local official clock time for any particular jurisdiction. By clock time, midnight is the opposite of noon, differing from it by 12 hours.

Solar midnight is the time opposite to solar noon, when the Sun is closest to the nadir, and the night is equidistant from sunset and sunrise. Due to the advent of time zones, which regularize time across a range of meridians, and daylight saving time, solar midnight rarely coincides with 12 midnight on the clock. Solar midnight depends on longitude and time of the year rather than on time zone. In ancient Roman timekeeping, midnight was halfway between dusk and dawn (i.e., solar midnight), varying according to the seasons.

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Antisolar point in the context of Earth's shadow

Earth's shadow (or Earth shadow) is the shadow that Earth itself casts through its atmosphere and into outer space, toward the antisolar point. During the twilight period (both early dusk and late dawn), the shadow's visible fringe —sometimes called the dark segment or twilight wedge—appears as a dark and diffuse band just above the horizon, most distinct when the sky is clear.

Since the angular diameters of the Sun and the Moon as viewed from Earth's surface are almost the same, the ratio of the length of Earth's shadow to the distance between Earth and the Moon will be almost equal to the ratio of the diameters of Earth and the Moon.

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Antisolar point in the context of Belt of Venus

The Belt of Venus, also called Venus's Girdle, the antitwilight arch, or antitwilight, is an atmospheric phenomenon visible shortly before sunrise or after sunset, during civil twilight. It is a pinkish glow that surrounds the observer, extending roughly 10–20° above the horizon. It appears opposite to the afterglow, which it also reflects.

In a way, the Belt of Venus is actually alpenglow visible near the horizon during twilight, above the antisolar point. Like alpenglow, the backscatter of reddened sunlight also creates the Belt of Venus. Though unlike alpenglow, the sunlight scattered by fine particulates that cause the rosy arch of the Belt shines high in the atmosphere and lasts for a while after sunset or before sunrise.

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