Astronomska skupina Fakultete za matematiko in fizilo Univerze v Ljubljani
Teleskop Vega

SLIKANJE DARK FRAME-ov (03.04.2006)

Naša skupina si je zadala nalogo:

  1. izmeriti temperaturno odvisnost temnega toka
  2. izmeriti odvisnost temnega toka od časa ekspozicije

Primerjava dark frame, ki smo ga naredili za celoten CCD čip (4096x4096) in za majhen kos čipa (512x512):

IMAGEMEANMINMAX
dark-10C_1s_512px.fits136.50.1128.
dark-10C_1s_4096px.fits136.60.1904.
dark-10C_5s_512px.fits135.70.458.
dark-10C_5s_4096px.fits136.70.6218.
dark-10C_10s_4096px.fits136.80.8816.
dark-10C_10s_512px.fits136.10.720.
dark-10C_30s_512px.fits136.60.1832.
dark-10C_30s_4096px.fits137.20.11976.
dark-10C_60s_512px.fits138.10.3400.
dark-10C_60s_4096px.fits138.60.16368.
dark-10C_120s_512px.fits139.80.6402.
dark-10C_120s_4096px.fits140.30.16368.
dark-10C_300s_512px.fits145.60.12868.
dark-10C_300s_4096px.fits145.70.16368.
dark-10C_600s_512px.fits153.80.16368.
dark-10C_600s_4096px.fits155.30.16368.

ukaz: imstat *fits

ukaz: epar imstat

parametri: PACKAGE = imutil TASK = imstatistics

images = dark-10*40* List of input images
(fields = image,mean,stdev,min,max) Fields to be printed
(lower = INDEF) Lower limit for pixel values
(upper = INDEF) Upper limit for pixel values
(nclip = 0) Number of clipping iterations
(lsigma = 3.) Lower side clipping factor in sigma
(usigma = 3.) Upper side clipping factor in sigma
(binwidt= 0.1) Bin width of histogram in sigma
(format = yes) Format output and print column labels ?
(cache = no) Cache image in memory ?
(mode = ql)

izhod: ctrl d ali :q.

Iz te tabelice lahko vidimo, da je vseeno, ali delamo s celim čipom ali pa le z delom čipa (stolpec MEAN). Posledično se odločimo, da delamo z majhnim področjem čipa, ker je bralni čas precej manjši!

No ja potem smo se odločili, da vseeno delamo obe velikosti. S tem bomo res lahko preverili ali je vseeno ali ne.

Ekspozicije: 1s, 5s, 10s, 30s, 60s, 120s, 300s, 600s.

Najprej smo se lotili darkov pri temperaturi -10oC. Začeli smo z velikostjo čipa 512x512. Nato pa še z velikostjo 4096x4096. Na zgornji tabeli vidimo, da bolje za nas, da delamo z manjšo velikostjo, saj nebi bili radi tu celo noč.

Nato smo ohladili čip na -15°C. In spet iste čase ekspozicij. Ocenjujemo, da temperatura ccd kamere niha z amplitudo približno 1°C.

Čip smo ohladili še na -20°C, -25°C in -30°C. Temperatura je nihala z amplitudo približno 1°C. Vse slikice smo posneli za velikost čipa 512x512, pri enakih ekspozicijah kot prej.

Podatki za ostale temperature

T = -15°C

IMAGEMEANSTDVMINMAX
dark-15C_1s_512px.fits150.3106.10.16352.
dark-15C_5s_512px.fits136.6.340.328.
dark-15C_10s_512px.fits136.26.4760.516.
dark-15C_30s_512px.fits136.58.3120.1328.
dark-15C_60s_512px.fits137.12.180.2474.
dark-15C_120s_512px.fits138.521.040.4616.
dark-15C_300s_512px.fits141.545.310.9216.
dark-15C_600s_512px.fits148.88.970.15488.

T = -20°C

IMAGEMEANSTDVMINMAX
dark-20C_1s_512px.fits134.96.3870.164.
dark-20C_5s_512px.fits135.36.3890.232.
dark-20C_10s_512px.fits135.66.440.368.
dark-20C_30s_512px.fits135.77.0210.864.
dark-20C_60s_512px.fits136.39.2770.1620.
dark-20C_120s_512px.fits137.114.020.2930.
dark-20C_300s_512px.fits139.30.060.6692.
dark-20C_600s_512px.fits152.7122.70.16368.

T = -25°C

IMAGEMEANSTDVMINMAX
dark-25C_1s_512px.fits140.36.050.7656.
dark-25C_5s_512px.fits135.46.370.212.
dark-25C_10s_512px.fits135.36.3890.256.
dark-25C_30s_512px.fits135.66.5730.548.
dark-25C_60s_512px.fits136.17.2450.968.
dark-25C_120s_512px.fits136.59.9980.1828.
dark-25C_300s_512px.fits138.222.010.4772.
dark-25C_600s_512px.fits140.339.220.8162.

T = -30°C

IMAGEMEANSTDVMINMAX
dark-30C_1s_512px.fits138.729.070.6176.
dark-30C_5s_512px.fits135.6.3770.168.
dark-30C_10s_512px.fits135.26.3770.210.
dark-30C_30s_512px.fits135.76.4310.404.
dark-30C_60s_512px.fits136.6.6920.626.
dark-30C_120s_512px.fits136.7.9090.1184.
dark-30C_300s_512px.fits136.514.10.2848.
dark-30C_600s_512px.fits138.325.770.5362.

Slikica prikazuje povprečje elektronov na 100 px v koloni pri temperaturi -10°C in ekspoziciji 10 s.

Slikica prikazuje povprečje elektronov na 100 px v koloni pri temperaturi -25°C in ekspoziciji 10 s.

Zadnja sprememba 04.04.2006 01:03 CEST
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Univerza v Ljubljani, F M F
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