All images described in this section start at pixel (700,1050).
The image sequence collected for the purpose of generating transfer curves and linearity curves did not cover the entire area of the CCD and therefore 5 smaller bias images were obtained, covering the same subraster as the flat-field images.
bias_1.fits Null 1.000 360 320 bias_2.fits Null 1.000 360 320 bias_3.fits Null 1.000 360 320 bias_4.fits Null 1.000 360 320 bias_5.fits Null 1.000 360 320
These images also show the same interference structure as the full-frame biases and a more pronounced glitch at the start of the overscan.
Table 3 lists the mean counts and standard deviation of each of these bias images.
Since the interference pattern is not coherent between images, difference images are not considered.
Therefore, the readout noise is taken as ADU.
18 pairs of flat-field images at various integrations times were taken in the sequence shown below.
tc_0.1_1.fits Null 0.100 360 320 tc_0.1_2.fits Null 0.100 360 320 tc_0.2_1.fits Null 0.200 360 320 tc_0.2_2.fits Null 0.200 360 320 tc_0.3_1.fits Null 0.300 360 320 tc_0.3_2.fits Null 0.300 360 320 tc_0.5_1.fits Null 0.500 360 320 tc_0.5_2.fits Null 0.500 360 320 tc_0.6_1.fits Null 0.600 360 320 tc_0.6_2.fits Null 0.600 360 320 tc_0.8_1.fits Null 0.800 360 320 tc_0.8_2.fits Null 0.800 360 320 tc_1.1_1.fits Null 1.100 360 320 tc_1.1_2.fits Null 1.100 360 320 tc_1.5_1.fits Null 1.500 360 320 tc_1.5_2.fits Null 1.500 360 320 tc_2.0_1.fits Null 2.000 360 320 tc_2.0_2.fits Null 2.000 360 320 tc_2.8_1.fits Null 2.800 360 320 tc_2.8_2.fits Null 2.800 360 320 tc_3.7_1.fits Null 3.700 360 320 tc_3.7_2.fits Null 3.700 360 320 tc_5.1_1.fits Null 5.100 360 320 tc_5.1_2.fits Null 5.100 360 320 tc_6.9_1.fits Null 6.900 360 320 tc_6.9_2.fits Null 6.900 360 320 tc_9.3_1.fits Null 9.300 360 320 tc_9.3_2.fits Null 9.300 360 320 tc_12.5_1.fits Null 12.500 360 320 tc_12.5_2.fits Null 12.500 360 320 tc_16.9_1.fits Null 16.900 360 320 tc_16.9_2.fits Null 16.900 360 320 tc_22.9_1.fits Null 22.900 360 320 tc_22.9_2.fits Null 22.900 360 320 tc_31.0_1.fits Null 31.000 360 320 tc_31.0_2.fits Null 31.000 360 320
For each of the pairs of frames, the integration time, mean counts and variance of the difference of the two frames (divided by two) were computed for the subregion (20:300,20:300) of the CCD image. The median stacked bias image was subtracted from each image before calculation. The results are listed in Table 4.
Figure 6 is the linearity curve and a straight line fit for the first of each pair of exposures. Extrapolating the fit to zero counts gives a negligible shutter delay, as expected, since the LED is controlled directly by the shutter controller and no mechanical shutter is involved. Saturation is not evident in this plot.
The transfer curve (using only the first of each pair for the X-axis, the second gives similar results) is shown in Figure 7 together with a straight line fit. Saturation is seen in the last point of the plot, which is therefore not used in the calculation of the conversion factor. The conversion factor is 2.31 electrons/ADU which yields a readout noise of 5.3 electrons/pixel.
Figure 8 shows the linearity curves expressed in terms of count rate versus exposure levels. Any nonlinearities present are at an amplitude of