Basic Parameters


Quantum Efficiency (%)


3500 4000 5500 7000 9000
Site#22b - QE   78   81  
Site#20b - QE   75   81  


Bias level and Readout Noise

Actually bias frames don't present any structure. Bias level and readout noise measured inside boxes of different sizes and on different parts of the frame give the same values than the full frame within the errors.
Next table show these values from last calibration runs.
A representative frame can be downloaded .

Site#22b (Blue) Site#20b (Red)
Date Bias RON Frame Bias RON Frame
ADUs e- ADUs e- ADUs e- ADUs e-
July 25 2000 234.7 250.0 4.6 4.9 fits file 217.4 184.8 4.9 4.2 fits file
Sept 24 2000 240.7 256.3 4.9 5.2 fits file 215.6 183.3 4.7 4.0 fits file
May 16 2001 248.1 263.7 3.6 3.8 fits file 233.9 199.0 4.6 3.9 fits file
Mar 05 2002 281.1 300.8 4.2 4.5 fits file 267.1 231.0 4.4 3.8 fits file
Jul 15 2002 288.9 309.1 4.3 4.6 fits file 275.6 238.4 4.4 3.8 fits file
Feb 04 2003 254.3 272.1 3.6 3.8 fits file 269.2 231.5 4.4 3.8 fits file
Mar 31 2003 254.5 272.3 4.4 4.7 fits file 269.0 231.3 4.1 3.5 fits file
June 06 2003 264.0 282.5 4.4 4.7 fits file 273.3 235.0 4.4 3.8 fits file
January 19 2006 268.2 285.6 5.9 6.2 fits file 277.2 235.6 4.2 3.6 fits file

No changes of bias level and readout noise have been founded when only a part of the CCDs (window) is read out. However, there are slightly changes of these values when reading is done in binning mode, mainly in X direction. See next table.

Binning Site#22b (Blue) Site#20b (Red)
Bias RON Bias RON
X Y ADUs e- ADUs e- ADUs e- ADUs e-
1 1 234.7 250.0 4.6 4.9 217.4 184.8 5.0 4.3
2 1 225.8 240.5 4.9 5.2 209.9 178.4 5.2 4.4
1 2 234.9 250.2 4.2 4.5 218.7 185.9 5.1 4.3
2 2 227.4 242.2 5.1 5.4 212.2 180.4 5.4 4.6
3 1 222.4 236.9 5.0 5.3 204.8 174.1 5.5 4.7
1 3 235.3 250.6 4.9 5.2 219.8 186.8 5.2 4.4
3 3 227.0 241.7 5.5 5.8 211.5 179.8 6.1 5.2
4 1 218.4 232.6 5.2 5.5 200.5 170.4 6.0 5.1


Dark Current

The mean signal measured in a set of 3600 secs. dark exposures is slightly higher than the bias level. These differences are significative. It's say, are higher than the variance between the bias frames taken in the same run.
Dark current for Site#22b is 0.00018 e-/sec (0.6 counts/hour) and for Site#20b is 0.00069 e-/sec (2.9 counts/hour).


Gain

The gain or conversion factor between electrons and counts can be calculated from the inverse of the slope when plotting variance versus signal. From two sets (blue and red) of internal lamp flat fields we have measured the variance and the signal inside boxes of different sizes and located in different parts of every frame. The values (e-/ADU) obtained from last calibration runs are:

Date Site#22b (Blue) Site#20b (Red)
July 25 2000 1.065   0.850  
Sept 24 2000 1.063   0.851  
May 17 2000 1.076   0.865  


Santos Pedraz Marcos
Last modified: January 17 2001