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Related to astronomical: Astronomical twilight, Astronomical Unit


Of or pertaining to astronomy or to observations of the celestial bodies. Also known as astronomic.

tropical year

tropical yearclick for a larger image
The period between two successive vernal equinoxes, the time the earth takes to complete one orbit around the sun relative to the first point of Aries. Its length was 365 days 5 h 48 min and 45.19 s in 2000, and it is changing by 0.00000006162 x y days (y in Julian years from 2000), or about 5 milliseconds/year. The tropical year differs from the solar year by 1 part in 26,000, since this is the period of the earth's precession about its rotational axis combined with the precession of the perihelion of the earth's orbit. Also called an astronomical, equinoctial, natural, or solar year. It contains one complete cycle of seasons.


The period of incomplete darkness following sunset and preceding sunrise. Twilight is designated as civil, nautical, or astronomical, as the darker limit occurs when the center of the sun is 6°, 12°, and 18°, respectively, below the celestial horizon. The period of civil twilight before sunrise is known as morning civil twilight and after the sunset as evening civil twilight. The air almanac lists the local mean times of the beginning of morning civil twilight and the end of evening civil twilight in exactly the same format as sunrise and sunset tables. The twilight tables are printed on the right-hand pages facing the sunrise and sunset tables, with each pair covering the same block of calendar dates.
References in periodicals archive ?
2018 DE1 will fly at a distance of 0.03254 astronomical units or about 3 million miles from the Earth's center.
HTF MI Analyst have added a new research study on Title "Global Astronomical Telescope Market Status (2015-2019) and Forecast (2020-2024) by Region, Product Type & End-Use" with detailed information of Product Types [, Refracting Telescope, Reflector Telescope & Catadioptric Telescope], Applications [Enter-level, Intermediate Level & Professional Research] & Key Players Such as Celestron, Meade, Vixen Optics, TAKAHASHI, ASTRO-PHYSICS, Bushnell, Bresser, ORION, Barska, Sky Watcher, Bosma, SharpStar, Visionking & TianLang etc.
Therefore, sighting the moon on this day is very difficult with the naked eye but possible by astronomical telescopes,' it stated.
The NAOJ and other astronomical organizations called on companies to use materials that do not reflect as much sunlight and to adjust the types of radio waves they use, among other actions.
members of the society, creating an astronomical environment that helps students develop
According to the president of the Astronomical Society, Hichem Ben Yahia, Amjed Mouelhi who is only 30 years old is preparing an exhibition on astronomical imagery to be held in March 2019.
The Slovak astronomical clock was unveiled on July 18, 2009, as part of the reconstruction of the square in 2004.
His Highness added that the countries classified as the first category are of lesser importance in the membership of the International Astronomical Union and are given the status of "observer" only.
The astronomical phenomenon is important because it's a good chance to observe four planets together and click nice photographs with the suitable equipment.
Deputy Director of the Association Abdelaziz Snobar told SANA that the Association isn't responsible for setting the dates of the lunar months of the Hijri calendar in Syria as this is the responsibility of the First Sharia Judge in Damascus, and the Association only provides scientific and astronomical studies to help him make the decision.
The correct, original definition is that a Blue Moon is the third full Moon in an astronomical season with four full Moons.
Abu Dhabi: The latest and largest astronomical observatory in the region was inaugurated recently in Abu Dhabi to spread scientific education and serve different segments of society.