At high latitudes, the Sun will not be lower than 12° below the horizon for a period in summer, and will not rise above 12° below the horizon for a period in winter. Solar Noon at Night during a polar night: Between 84°34' and 90° North or South. Civil twilight is the period when enough natural light remains that artificial light is not needed.
'All Intensive Purposes' or 'All Intents and Purposes'? The collateral adjective for twilight is crepuscular, which may be used to describe the behavior of animals that are most active during this period. , Three subcategories of twilight are established and widely accepted: civil twilight (brightest), nautical twilight, and astronomical twilight (darkest).. Mary has a liberal arts degree from Goddard College and Nautical Twilight: the time when the center of the sun is 12 degrees below the horizon, and only general or vague outlines of objects are visible. People usually need headlights to drive and artificial light to work outdoors during nautical twilight. after astronomic dawn or before astronomic dusk). Twilight on Earth is the illumination of the lower atmosphere when the Sun is not directly visible because it is below the horizon. , Astronomical dawn is the moment when the geometric center of the Sun is 18 degrees below the horizon in the morning. "Civil Twilight" "6°", "Nautical Twilight" "12°". Outside the polar circles, where the angular distance from the polar circle is less than the angle which defines twilight (see above), twilight can continue through local midnight near the summer solstice.
People refer to this time of day as “nautical twilight” to reference the fact that sailors often took navigational observations during this time, since the visibility was ideal.
At the equator, civil twilight can last as little as 24 minutes. At night, nautical twilight is sometimes called “nightfall,” referencing the fact that the sky is rapidly starting to darken, and it is soon going to be so dark that artificial light will be a necessity. Such statutes typically use a fixed period after sunset or before sunrise (most commonly 20–30 minutes), rather than how many degrees the sun is below the horizon. As one gets closer to the Arctic and Antarctic circles, the sun's disk moves toward the observer's horizon at a lower angle. In the morning, people may refer to nautical twilight as “first light,” the period when light first begins to be visible and the sky slowly starts to flush with color as the sun comes up.
The observer's earthly location will pass through the various twilight zones less directly, taking more time. Astronomical dusk is the moment when the geometric center of the Sun is 18 degrees below the horizon in the evening. Under good atmospheric conditions with the absence of other illumination, during nautical twilight, the human eye may distinguish general outlines of ground objects but cannot participate in detailed outdoor operations. Define begin morning nautical twilight. In Christian practice, "vigil" observances often occur during twilight on the evening before major feast days or holidays. What made you want to look up nautical twilight?
, Nautical twilight has military considerations as well. Lowest latitude can be observed at local midnight in month of April: Lowest latitude can be observed at local midnight in month of May: Lowest latitude can be observed at local midnight in month of October: Lowest latitude can be observed at local midnight in month of November: These are the largest cities of their respective countries where the various twilights can continue through local solar midnight: Although Helsinki, Oslo, Stockholm, Tallinn, and Saint Petersburg also enter into nautical twilight after sunset, they do have noticeably lighter skies at night during the summer solstice than other locations mentioned in their category above, because they do not go far into nautical twilight. These latitudes include many densely populated regions of the Earth, including the entire United Kingdom and other countries in northern Europe and even parts of central Europe.
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Examples include the following periods: when drivers of automobiles must turn on their headlights (called lighting-up time in the UK); when hunting is restricted; when the crime of burglary is to be treated as nighttime burglary, which carries stiffer penalties in some jurisdictions. By analogy with evening twilight, the word twilight is also sometimes used metaphorically, to imply that something is losing strength and approaching its end.
Morning nautical twilight begins (nautical dawn) when the geometric center of the sun is 12 degrees below the horizon in the morning and ends when the geometric center of the sun is 6 degrees below the horizon in the morning. Twilight is important in Islam as it determines when certain universally obligatory prayers are to be recited.
civil dawn) and EECT (end evening civil twilight, i.e. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight.
According to Hindu scriptures, a daemonic king, Hiranakashipa, performed penance and obtained a boon from Brahma that he could not be killed during day or night and neither by human nor animal. What an interesting article. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). civil dusk) are used to refer to the start of morning civil twilight and the end of evening civil twilight, respectively. Nautical twilight is a period in the morning and evening when the sun is between six and 12 degrees below the horizon. A white night is a night with only civil twilight which lasts from sunset to sunrise.. Evening astronomical twilight begins when the geometric center of the sun is 12° below the horizon in the evening and ends (astronomical dusk) when the geometric center of the sun is 18° below the horizon in the evening.
In general, the term nautical twilight refers to sailors being able to take reliable readings via well known stars because the horizon is still visible, even under moonless conditions. I have heard that places in Alaska and the Arctic region are in perpetual twilight for certain times of the year. These are not the types of vampires that sparkle in the sunlight...oh no, these are the superhuman creatures that kill at will to suck blood. For example, very old people may be said to be "in the twilight of their lives". In some places (away from urban light pollution, moonlight, auroras, and other sources of light), where the sky is dark enough for nearly all astronomical observations, astronomers can easily make observations of point sources such as stars both during and after astronomical twilight in the evening and both before and during astronomical twilight in the morning.  In the US, civil twilight for aviation is defined in Part 1.1 of the Federal Aviation Regulations (FARs) as the time listed in the American Air Almanac.. Because of light pollution, observers in some localities, generally in and near large cities, may never have the opportunity to view anything but the brightest stars, irrespective of the presence of any twilight at all, nor to experience anything close to a truly dark sky.
Specific information about twilight times and length is usually provided in sunrise-sunset charts issued by organizations which provide weather information.
Which of the following is a fruit named after a Moroccan seaport. If you are into horror movies, you should check this one out. [a] North Pole has the experience of this from November 13 to January 29. Midsummer twilight over Rainbow Ridge, Landers, California. , Nautical dawn is the moment when the geometric center of the Sun is 12 degrees below the horizon in the morning. As observed from the Earth (see apparent magnitude), sky-gazers know Venus, the brightest planet, as the "morning star" or "evening star" because they can see it during civil twilight.. This angle of the sun's motion with respect to the horizon changes with latitude as well as the time of year (affecting the angle of the Earth's axis with respect to the sun).
Nautical Twilight: Begins in the morning, or ends in the evening, when the geometric center of the sun is 12 degrees below the horizon. Nautical twilight definition is - the period before sunrise or after sunset during which the sun is not more than 12 degrees below the horizon. At the winter solstice within the polar circle, twilight can extend through solar noon at latitudes below 72.561° (72°33′43″) for civil twilight, 78.561° (78°33′43″) for nautical twilight, and 84.561° (84°33′43″) for astronomical twilight. This occurs for one day at latitudes near 9 degrees from the Pole and extends up to several weeks the further towards the Pole one goes. nautical dusk) are used and considered when planning military operations. by "standing to", in which everyone assumes a defensive position. nautical dawn) and EENT (end evening nautical twilight, i.e. I used to live in Vermont, and there was a place I would go to watch the sunset. At latitudes greater than 48°34' North or South, on dates near the summer solstice, twilight can last from sunset to sunrise, since the Sun does not go more than 18 degrees below the horizon, so complete darkness does not occur even at solar midnight.
At latitudes within 9 degrees of either Pole, as the sun's angular elevation difference is less than 18 degrees, twilight can last for the entire 24 hours. However, in other places, especially those with skyglow, astronomical twilight may be almost indistinguishable from night.  Evening civil twilight begins at sunset and ends when the geometric center of the sun reaches 6° below the horizon. For example, the twilight of Friday is reckoned as Sabbath eve, and that of Saturday as Sabbath day; and the same rule applies to festival days.
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