An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 25 Search : circle
reflecting circle
  دایره‌ی ِ بازتابی   
dâyere-ye bâztâbi

Fr.: cercle à réflexion   

An instrument for measuring angular distances, based on the same principle as the → octant, but with a full circular limb divided into 720°. It was invented in 1752 by the German astronomer Johann Tobias Mayer (1723-1762) to improve on the octant which often gave wrong results because of incorrect graduations. The instrument consisted of an index arm and a small telescope, both pivoted centrally. In practice, the index arm is first set to zero, and the telescope rotated until the two images of a star are seen in coincidence (the one directly, the other by double reflection). Then the index arm is freed, and rotated until the other object is seen in coincidence after double reflection. The angle has now been measured, but the double operation is repeated several times, and the final angle divided by the number of repetitions to find a mean value. Hence, the instrument was sometimes called a "repeating circle." The reflecting circle had little success because it was heavy and uncomfortable to use. Its improved form is called → Borda circle.

reflection; → circle.

setting circles
  دایره‌های ِ آماج‌گیری   
dâyerehâ-ye âmaj-giri

Fr.: cercles de pointage   

Two graduated disks attached to the right ascension and declination axis of an equatorial mount used in amateur astronomy that help an observer find astronomical objects in the sky by their equatorial coordinates.

M.E.; O.E. settan "cause to sit, put in some place, fix firmly" (cf. O.N. setja, O.Fris. setta, Du. zetten, Ger. setzen); → circle.

Dâyeré, → circle; âmâj-giri "taking aim," from âmâj "aim, target," → point + giri "taking" (vebal noun of gereftan "to take, seize, hold;" Mid.Pers. griftan, gir- "to take, hold, restrain;" O.Pers./Av. grab- "to take, seize," cf. Skt. grah-, grabh- "to seize, take," graha- "seizing, holding, perceiving," M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE *ghrebh- "to seize").

squaring the circle
  چاروشش ِ پرهون، ~ ِ دایره   
cârušeš-e parhun, ~ dâyeré

Fr.: quadrature du cercle   

Same as → quadrature of the circle

square; → wave.

transit circle
  پرهونِ گذر، ~ِ نیمروزانی   
parhun-e gozar, ~ nimruzâni

Fr.: cercle méridien   

An observing instrument provided with a graduated vertical scale, used to measure the declinations of heavenly bodies and to determine the time of meridian transits. Same as → meridian circle.

transit; → circle; nimruzâni, adj. of nimruzân, → meridian.

vertical circle
  پرهون ِ هجین، دایره‌ی ِ ~   
parhun-e hajin, dâyere-ye ~

Fr.: cercle vertical   

The greater circle on the celestial sphere which passes through → zenith, → nadir, and the star and whose plane is perpendicular to the plane of horizon. Same as → azimuth circle.

vertical; → circle.


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