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: 6 Search : imaging
angular differential imaging (ADI)
  تصویرگری ِ دگرسانه‌ای ِ زاویه‌ای   
tasvigari-ye degarsâne-yi-ye zâviye-yi

Fr.: imagerie différentielle angulaire   

A high-contrast imaging technique that reduces minute temporal and spatial → seeing fluctuations and facilitates the detection of faint point sources, in close separation from their stars. It consists of the acquisition of a sequence of images with an → altazimuth mounting telescope while the instrument field derotator is switched off. This keeps the instrument and telescope optics aligned and allows the field of view to rotate with respect to the instrument. For each image, a reference → point spread function (PSF) is constructed from other appropriately selected images of the same sequence and subtracted to remove quasistatic PSF structure (Marois et al. 2006, ApJ 641, 556).

angular; → differential; → imaging.

imaging
  تصویرگری   
tasvirgari (#)

Fr.: imagerie   

The visual representation of an astronomical body using a two-dimensional detector and computerized techniques.

From → image + → -ing.

Tasvirgari, from tasvirgar agent noun from tasvirimage + -gar from kar-, kardan "to do, to make" (Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build;" Av. kərənaoiti "makes;" cf. Skt. kr- "to do, to make;" krnoti "makes," karma "act, deed;" PIE base kwer- "to do, to make").

Imaging Atmospheric Cherenkov Technique (IACT)
  تشنیک ِ تصویرگری ِ چرنکوف ِ جوی   
tašnik-e tasvirgiri-ye Čerenkov-e javvi

Fr.: téchnique d'imagerie Čerenkov atmosphérique   

The method used to detect very brief flashes of → Cherenkov radiation generated by the → cascade shower of → relativistic charged particles produced when a very high-energy → gamma ray (in the range 50 GeV to 50 TeV) strikes the atmosphere at a typical altitude of 10 km. Owing to this technique, it possible to discriminate cosmic gamma rays from the cosmic ray background and to determine their energy and source direction. More specifically, the incoming gamma-ray photon undergoes → pair production in the vicinity of the nucleus of an atmospheric molecule. The electron-positron pairs produced are of extremely high energy and immediately radiate in a → bremsstrahlung process. This radiation is itself extremely energetic, with many of the photons undergoing further pair production. A cascade of charged particles ensues which, due to its extreme energy, produces a flash of Cherenkov radiation lasting between 5 and 20 nano-seconds. The total area on the ground illuminated by this flash corresponds to many hundreds of square meters, which is why the effective area of IACT telescopes should be large.

imaging; → atmospheric; → Cherenkov; → technique.

imaging detector
  آشکارگر ِ تصویرگری   
âškârgar-e tasvirgari

Fr.: détecteur d'image   

A detector with two-dimensional capability, such as a CCD.

image; → → scale.

infrared imaging
  تصویرگری ِ فروسرخ   
tasvirgari-ye forusorx (#)

Fr.: imagerie infrarouge   

Imaging with an infrared detector.

infrared; → imaging.

sub-arcsecond imaging
  تصویرگری ِ زیر-ثانیه‌ای   
tasvir-gari-ye zir-sâniye-yi

Fr.:   

Imaging in excellent seeing conditions using an adequate detector to obtain stellar images whose profile lies in the sub-arcsecond range.

sub-arcsecond; → imaging.