David's Astronomy Pages CCD Image Notes - (2005-01-15)

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Goto Images from 2005-01-05

Dark Current Investigations

Whilst testing the CCD camera for any problems from water/dampness (due to exposure rain after loosing observatory roof during a severe gale) I took a series of 15 sec dark frames over the temperature range +27.4 to -4.8 deg C. From these frames the dark current counts associated with the primary peak, a secondary peak (that was observable at temperature warmer than 5 deg) and the hottest pixel where measured.  Equivalent measurements were made on previous 15 sec dark frames taken over the temperature range -14.8 to -30.2 degC.  Images showing the reduction in dark current with temperature is shown in the montage and graph below.

15 sec dark frames  2x2 binning, ST-7E ABG

Graph : 

Graph of Dark Current versus Temperature (+27.4 to -30.2 deg C range) Note how dark current increases with temperature. The ADU of hottest picture is plotted at x50 scale,  it can be seen that  the CCD becomes non-linear at ADU counts above 33000)

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