3/11/2024 0 Comments Civil dusk definition![]() God knew that you used to betray your souls, and He has redeemed you, and has pardoned you. They are the keepers of your secrets, and you are the keepers of their secrets. The most frequently-encountered use of the term is to apply it to certain species of insects that are most active during that time.Permitted for you is sexual intercourse with your wives during the nights of fasting. The collateral adjective of "twilight" is crepuscular (for daylight it is "diurnal" and for night, "nocturnal"). At temperate-zone latitudes, twilight is shortest at or near both equinoxes, slightly longer around the time of the winter solstice, and much longer in late spring and early summer. This is due to the fact that at low latitudes the earth spins the fastest and therefore the sun spends less time near the horizon while in polar regions the sun's path in the sky is smaller and thus spends more time near the horizon. The length of twilight after sunset and before sunrise is heavily influenced by the latitude of the observer in the Arctic and Antarctic regions, twilight (if at all) can last for several hours (with none at the poles within a month on either side of the winter solstice), while at the equator, it can go from day to night in as little as 20 minutes. Astronomical twilight can last all night for several weeks as far from the poles as 50°N or S. Above roughly 60°N or S, civil twilight lasts all night at midsummer, while above about 55°N or S, nautical twilight lasts all night at midsummer. ![]() In high latitudes outside the polar circles, 24-hour daylight is not seen, but twilight extends from sunset to sunrise, a phenomenon often referred to as ' white nights'. Within the polar circles, 24-hour daylight is encountered in summer. (For these definitions, we use an ideal horizon 90° from the zenith.) Conceptually, the dimmest stars ever visible to the naked eye - those of the sixth magnitude - will appear in the evening once the sun falls more than 18° below the horizon and disappear when the sun moves to within 18° of the horizon in the morning however, due to photopollution, some localities - generally those in large cities - may never have the opportunity to view even fourth-magnitude stars, irrespective of the presence of any twilight at all. ![]() Most casual observers would consider the entire sky already fully dark at the limit of astronomical twilight, and astronomers can easily make observations of point sources such as stars, but faint diffuse objects such as nebulae and galaxies can only be properly observed beyond the limit of astronomical twilight. Astronomical twilight is defined as the time when the centre of the refracted disk of the sun is more than 12° below the horizon but less than 18°.The end of this period in the evening, or its beginning in the morning, is also the time at which traces of illumination near the sunset or sunrise point of the horizon are very difficult if not impossible to discern (this often being referred to as "first light" before dawn and "nightfall" after dusk). This is the time when sailors can take reliable star sights of well known stars, using a visible horizon for reference. ![]()
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