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Lancement : Menu [Analyse] > [Test/Caractérisation de CCD] > [Courant thermique]

Cette fonction n'est pas accessible depuis la version light. Afin de pouvoir l'utiliser, il est nécessaire d'obtenir une clé "version complète" pour le logiciel.

But : Connaître le courant thermique de son CCD.

As input image data, at least 3 images in total darkness has to be achieved, having the same exposure time for each (from 5 minutes to 2 hours depending on the cooling efficiency and CCD temperature).

A mean clean Offset or Bias image MUST to be done as the result of the median stack of many individual bias frames. Also the conversion factor must be known accurately.

Be aware that sometimes residual image can disturb dark current measurement, especially if the CCD is cooled at -120C . Avoid to acquire the data just after having acquired high level flat fields. To watch this out : take ten dark frames at the same temperature and check whether or not the mean dark level is decreasing. Wipe the CCD many times before in the darkness. For instance take 10 darks exposure of one hour exposure, and do not use the first images (do not select the first four images).

La zone de calculs X₁, X₂, Y₁, Y₂  devra être exempte de graves défauts, comme une colonne chaude.

Voici les résultats renvoyés par le logiciel:

Ceci est la moyenne des lignes projetées sur une colonne. On voit ici les effets dus aux colonnes défectueuses...

Ici les pixels chauds signalés par une croix verte sur l'image, au dessus de 5 sigmas.

Résultats renvoyés par la fonction Loading :F:\Images\Frankie\dark\run1@-120\dark0004.fits
Pixel size information NOT present or NULL in file header, so I take : 15 x 15(µm)
Loading :F:\Images\Frankie\dark\run1@-120\dark0003.fits
Loading :F:\Images\Frankie\dark\run1@-120\dark0002.fits
Loading :F:\Images\Frankie\dark\run1@-120\NoiseMedian.cpa
Integer data type...
Median search :
Compute median frame...
Pixel amount taken to provide median frame :
dark0004.fits ->1  27.92%
dark0003.fits ->2  44.71%
dark0002.fits ->3  27.37%
Offset -> Mean :327.1 Median : 327 ADU
Exposure time (s) =  1800
Dark current : 1.333 ± 0.4714 ADU
Dark current : 5.333 ± 1.886 e-/hour/pixel
Cosmic event rate : 1.195 ± 0.04297 events/min/cm²
Pixel amount above 5 sigmas : 10659 threshold (ADU) : 10.51
Dark current using median frame after median filtering : 5.128 e-/hour/pixel

Methods used :

The software compute a median stack out of the N provided images and subtract the bias file to it. The dark current is the remaing amount of adus above the bias image (positive data). the defects are subtracted automatically as the difference between individual frames and the median stacked frame.

Focntion script associée :
GetDark

Images de test :
Images de test

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