An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 5 Search : crescent
crescent
  هلال، برن   
helâl (#), barn (#)

Fr.: croissant   

The figure of the → Moon or an → inferior planet when it is less than half illuminated, as seen by the → observer.

From O.Fr. croissant, from L. crescentum, p.p. of crescere "to grow, increase; spring forth," from PIE base *ker- "to grow" (cf. Gk. kouros "boy," kore "girl," Pers. dialects Laki korr "son, boy," Lori kor "son, boy," Malayeri kora "boy," Kordi kur "son," Arm. serem "bring forth," serim "be born").

Helâl from Ar. Barn "the new moon," from Proto-Iranian *aparnâ- "unfilled," from negation prefix → a- + parnâ- "full;" cf. Mid.Pers. purr mâh "full moon," Av. pərənô-mâh- "full moon," Skt. purna-mâs- "full moon;" → full; → moon.

crescent Moon visibility
  دیاری ِ هلال ِ ماه   
diyâri-ye helâl-e mâh

Fr.: visibilité du croissant lunaire   

The first sighting of the → New Moon after its → conjunction with the Sun. Although the date and time of each New Moon can be computed exactly, the visibility of the lunar → crescent as a function of the → Moon's age depends upon many factors and cannot be predicted with certainty. The sighting within one day of New Moon is usually difficult. The crescent at this time is quite thin, has a low surface brightness, and can easily be lost in the → twilight. Generally, the lunar crescent will become visible to suitably-located, experienced observers with good sky conditions about one day after New Moon. However, the time that the crescent actually becomes visible varies from one month to another. The visibility depends on sky conditions and the location, experience, and preparation of the observer. Ignoring atmospheric conditions, the size and brightness of the lunar crescent depend on the → elongation which in turn depends on several factors: 1) The Moon's elongation at New Moon (the elongation of the Moon at New Moon is not necessarily 0). 2) The speed of the Moon in its elliptical orbit. 3) The distance of the Moon, and 4) The observer's location (parallax). The combined effect of the first three factors gives geocentric elongation of the Moon from the Sun at an age of one day which can vary between about 10 and 15 degrees. This large range of possible elongations in the one-day-old Moon is critical (US Naval Observatory).

crescent; → moon; → visibility.

crescent width
  پهنای ِ هلال، ~ برن   
pahnâ-ye helâl, ~ barn

Fr.: largeur de croissant   

The width of the lit area of the → Moon measured along the Moon's diameter.

crescent; → width.

waning crescent
  هلال ِ کاهنده، برن ِ ~   
helâl-e kâhandé, barn-e ~

Fr.: croissant descendant   

The crescent phase of the moon following the → last quarter.

waning; → crescent.

waxing crescent
  هلال ِ فزاینده، برن ِ ~   
helâl-e fazâyandé, barn-e ~

Fr.: croissant montant   

The phase of the Moon between the → new moon and the → first quarter.

waxing; → crescent.