EFOSC2 CCD40 quality control and measurements

Check on CCD40 GAIN and readout noise (RON)

Brief summary : the values for GAIN and RON in the EFOSC2 headers are incorrect, and the summary table on the EFOSC2 webpage also has the wrong values. Our measurements on CCD#40 agree with the ESO CCD quality control pages. Hence it appears to be a problem with the propagation of information. To be clear - the wrong GAIN and RON numbers are written into the EFOSC2 file headers on creation at La Silla (and are in the archived versions). Also the RON appears to be increasing which is in agreement with the ESO quality control measurements. It has recently increased from 11e- to 12.8e-. 

We always use NORMAL readmode and 2x2 binning (which is Mode32). 

During 6 PESSTO nights in October 2012. GAIN and RON measured using the IRAF findgain task (by M. Fraser, 20130522) :
Gain = 1.18 electrons per ADU Read noise = 11.08 electrons
Gain = 1.18 electrons per ADU Read noise = 11.00 electrons
Gain = 1.17 electrons per ADU Read noise = 10.98 electrons
Gain = 1.17 electrons per ADU Read noise = 10.91 electrons
Gain = 1.18 electrons per ADU Read noise = 10.89 electrons
Gain = 1.18 electrons per ADU Read noise = 11.18 electrons
Average measured GAIN = 1.18 e-/ADU
Average RON = 11.00 e-

During 6 PESSTO nights in April 2013. GAIN and RON measured using the IRAF findgain task: 
Gain = 1.18 electrons per ADU Read noise = 12.89 electrons
Gain = 1.18 electrons per ADU Read noise = 12.54 electrons
Gain = 1.18 electrons per ADU Read noise = 12.54 electrons
Gain = 1.18 electrons per ADU Read noise = 12.57 electrons
Gain = 1.17 electrons per ADU Read noise = 11.37 electrons
Gain = 1.17 electrons per ADU Read noise = 11.32 electrons
Average measured GAIN = 1.18 e-/ADU
Average RON = 12.21 e-

First year PESSTO trends 
The plots below show the bias level, readnoise and gain values for the CCD#40 over one year. Measurements done by Morgan Fraser at QUB (7/6/2013). 
The methods are described in the PESSTO data release paper in prep (Smartt et al. A&A). 

The major issue 


In EFOSC2 headers, the values in the files created on La Silla (and of course in the archive) are set incorrectly. This is what they are set to in ALL EFOSC2 files for normal readout and 2x2 binning. 

HIERARCH ESO DET OUT1 GAIN = 0.91 / Conversion from electrons to ADU
HIERARCH ESO DET OUT1 RON = 7.80 / Readout noise per output (e-)

Our measurements for the GAIN are in good agreement with those reported on the EFOSC2 quality control pages (RON=11.18 e- and GAIN=1.18 ; taken on 20130521)

http://www.ls.eso.org/sci/facilities/lasilla/sciops/CCDs/EFOSC2/CCD.40.nl2x2.html

But the summary table on the EFOSC2 webpage is also out of date :

http://www.eso.org/sci/facilities/lasilla/instruments/efosc/inst/Ccd40.html




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