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1) parsunidan; 2) âbizidan
Fr.: préciser, spécifier
1) To mention or name specifically or definitely; state in detail.
A part or an individual taken as exemplifying a whole mass or number; a typical animal, plant, mineral, part, etc. → sample.
From L. specimen "mark, example, indication, sign, evidence," from speci- stem of specere "to look at," → -scope, + -men noun suffix denoting result or means.
Nemuné, from nemudan "to show;" Mid.Pers. nimūdan, nimây- "to show," from O.Pers./Av. ni- "down; in, into," → ni- (PIE), + māy- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure."
An image defect, one of a large number of bright and dark spots, that
appears when an object is illuminated by monochromatic, highly
→ coherent light.
This phenomenon results from the → interference
of a number of randomly phased complex contributions of electromagnetic
→ wavefronts scattered from an object with
rough structure, such as a piece of paper, a display screen, or a metallic surface.
In particular, whenever the object is rough on the scale of an optical
wavelength, the image has a grainy appearance.
Also called speckle noise.
Speckle "a speck or small spot, as a natural dot of color on skin, plumage, or foliage," from M.E.speck (from O.E. specca "small spot, stain," of unknown origin; probably related to Du. speckel "speck, speckle") + -le a noun suffix having originally a diminutive meaning.
Pakâl, from pak "spot" (Lâri, Gerâši), pašy "mingled, confused" (Tâleši), probably related to pisé "dappled, variegated," pis, pisi "leprosy," neveštan "to write," pišé "profession," → professional astronomer; Mid.Pers. parš "speckled, spotted," pēsīdan "to color, adorn," pēsit "adorned;" O.Pers. pais- "to adorn, cut, engrave;" Av. paēs- "to paint, adorn," paēsa- "adornment;" cf. Skt. peś- "to adorn, hew out, decorate," piśáti "adorns; cuts;" Gk. poikilos "multicolored;" L. pingit "embroiders, paints;" O.C.S. pisati "to write;" O.H.G. fēh "multicolored;" Lith. piēšti "to draw, adorn;" PIE base *peik- "colored, speckled."
Fr.: interférométrie des tavelures
A technique for generating a clear composite image of a celestial object blurred by → atmospheric turbulence in which a large number of short-exposure photographs are mathematically correlated by a computer. By comparing the behavior of the → speckles in a series of images it is possible to approach the theoretical resolution of the telescope.
Fr.: durée de vie de tavelures
The time scale on which a stellar image changes significantly due to → atmospheric turbulence. It is proportional to the ratio r0/Δv, where r0 is the → Fried parameter and Δv the standard deviation of the distribution of wind velocities weighted by the turbulence structure coefficient. Typical lifetimes in the visible range from about 3 to 30 milliseconds.
Omr "life-time;" from Ar. 'umr; pakâl, → speckle.
Fr.: bruit de tavelures
An image defect associated with the → speckle phenomenon.
Of or pertaining to a → spectrum.
radebandi-ye binâbi (#)
Fr.: classification spectrale
A system that assigns a → spectral type to a star according to characteristics of its spectrum. The earliest attempt to divide stars on the basis of their spectra was the → Secchi classification in the 1860s. This scheme paved the way for the → Harvard classification that led to the current → Morgan-Keenan classification of spectral types. In the Harvard system stars were originally thought to follow an evolutionary sequence from the "early" O and B types to the "late" K and M types. Although this is now known to be wrong, the terms → early-type star and → late-type star are still in use. In the Morgan-Keenan system stars are classified as type O, B, A, F, G, K, or M in order of decreasing → effective temperature, and each type further subdivided into subclasses from 0 (hottest, except for → O-type stars) to 9 (coolest). They are also accompanied by a → luminosity class. In the late 1990s, spectral types L and T were added to the sequence to accommodate the coolest stars and → brown dwarfs (with class Y reserved for the coolest brown dwarfs of all, as yet unobserved).
Fr.: couverture spectrale
Fr.: densité spectrale
For a specified → bandwidth of radiation consisting of a continuous → frequency spectrum, the total → power in the bandwidth divided by the bandwidth. Spectral density describes how the power (or variance) of a time series is distributed with frequency. Also called power spectral density.
Fr.: dispersion spectrale
spectral energy distribution (SED)
vâbâžeš-e kâruž-e binâbi
Fr.: distribution de l'énergie spectrale
A plot showing the energy emitted by a source as a function of the radiation
wavelength or frequency. It is used in many branches of astronomy to characterize
astronomical sources, in particular mainly in → near infrared
and → middle infrared to study
→ protostars or
→ young stellar objects. The SED of these objects is
divided in four classes.
ârang-e binâb, ~ binâbi
Fr.: motif spectral
An emission or absorption mark in the spectrum of an astronomical object, of known or unknown origin, usually with complex structure.
Fr.: indice spectral
1) The → exponent
of the → frequency on which depends
the intensity of the → continuum emission, that is:
The exponent (α) typically
takes positive values from 0 to 2 for → thermal emission,
while → non-thermal emission, such as
→ synchrotron radiation,
leads to negative values of the spectral index ranging from about -0.5 to -1.5.
Fr.: raie spectrale
A dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow wavelength range, compared with the nearby wavelengths.
Fr.: domain spectral
The observable spectral range provided by a spectroscope, as determined by the grating dispersion, camera focal length, and detector size.
Fr.: région spectrale
An extent of wavelengths into which the electromagnetic spectrum is divided; e.g. infrared or ultraviolet region.
vâgošud-e binâb, ~ binâbi
Fr.: résolution spectrale
The capacity of a spectrograph to separate two adjacent spectral lines. The theoretical spectral resolution depends on the grating dispersion, grating position, pixel size, collimator and camera focal length, and the entrance slit-width.
Fr.: réponse spectrale
Domain of the electromagnetic spectrum over which a detector is sensitive. Same as spectral sensitivity.
Fr.: série spectrale
Spectral lines or group of lines occurring in sequence.