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The command does a series of tests on a catalogue of flat frames.
The flat fields in the catalogue should be grouped in pairs with
the same exposure time. Most ideally, one should be two groups of
8 frames each - the first with increasing exposure times and the
second with decreasing exposure times, interleaved with those of
the first group. In this way, tends observed in the CCD response
that are probably caused by the effect of temperature variations
on the light source can be rejected.
The command requires a value for the mean bias level and the
standard deviation in the keywords BIASMEAN and BIASSIGM
to be filled and hence should be executed after the command
TESTB/CCD. If no value or the value zero is found no bias
offset will be subtracted. The command produces:
- A table containing the exposure time of the first of each
sets (frames 1); the exposure time of the second frames
(frames 2); the median pixel intensities over the selected
frame sections in frames 1; the median pixel intensities
over the selected area in frames 2; the variance of the
difference of the frames 1 and 2
- Two linearity curves, expressed as count rate versus true
exposure time. The mechanical shutter delay is determined
either by linear extrapolation of the normal linearity curve
(observed counts versus exposure time), thus assuming the
response of the CCD is linear, or by adjusting the exposure
times such that the count rate curve is closest to a
straight line, thus allowing for a first-order nonlinearity
in the response of the CCD.
- A transfer curve (Janesick et al., 1987) generated
for any window onto the images obtained.
The linearity and the transfer curves may be generated for
any section of the images.
Next: TESTD/CCD
Up: Test Commands
Previous: TESTF/CCD
Pascal Ballester
Tue Mar 28 16:52:29 MET DST 1995