[1:1060,300:700]) were used. These are from night 6 (whereas the dome flats used were from night 8). The bias images from night 6 are the ones which resembles the mean bias image the most.
findgain was used at the section
(center of CCD) and
[910:1030,080:200] (right hand side of CCD).
It was suspected, that the CCD would behave strange in the right hand side.
The result is shown in Figure .
It it seen that apparently CF increases with level.
However, this can not be the case since the CCD found to be linear
in the direct test, cf. Sect. below.
More probable a malfunction in the read-out electronics
caused RON to vary with the exposure level.
A direct way to calculate the RON in ADU is the fact, that the standard deviation on a bias image is the RON in ADU. The standard deviation of 5 raw bias images (dfsc1921-1925) was found to be 2.25 ADU (using imstat with an upper limit of 150 to cut cosmic-ray-events).
If we use only flat field images with levels above 1000 ADU and without severe cosmic-ray-events, we get CF = 1.95 e-/ADU and RON = 2.25 ADU. These are the values that have been used hereafter.
Properties of E and S0 Galaxies in the Clusters HydraI and Coma
Master's Thesis, University of Copenhagen, July 1997
Bo Milvang-Jensen (firstname.lastname@example.org)