VLT-MAN-ESO-14650-4942
P96
24.06.2015
90 of 161
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
Stability of the AGCCD
The stability of the imaging mode and the AG CCD detector was investigated.
Short, medium and long term stability aspects were tested.
a) The spectrophotometric standard star GD71 was monitored over 1 hour with exposures
every few seconds. The 1-s standard deviation in B and V bands are 0.006 magnitude for
both band. It represents a variation of 0.4%.
b) The stability at medium term was checked with the evolution of the bias and readout noise
levels. They are shown below. Over a period of 52 days, the RMS of the bias level variability
is 0.33% and for the RON it is 0.56%.
c) the long term stability of the instrument was tested with the spectrophotometric standard
star EG274 observed during a period of more than 500 days, However, the star was quite
often observed under sub-optimal condition (twilight with fast variable sky background, etc).
Nevertheless, the RMS is of 0.42% over 1.4 years.
d) the noise structure/background unfortunately follows the ambient temperature evolution. The
Peltier that cools down the detector is cooled down with a coolant flow. Unfortunately, if there is an
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