QAC_STATS: ngc0001.ccd -4.29944e-05 0.0126181 -0.0720263 0.0892035 0 -0.00437804that represent the mean, rms, min and max of a set of numbers. Optionally there are 2 or more numbers present: the flux and the signal ratio sratio=(psum+nsum)/(psum-nsum), where the sums are over the positive and negative values. For sratio=0 (or near 0) there is no signal, it’s mostly noise, whereas for sratio=1 (or near 1) it’s mostly signal.
It is used by a number of programs in NEMO, e.g. tabstat(1NEMO) and ccdstat(1NEMO) where the keyword qac=t needs to be used to active this style of output.
Of course all of the interesting science happens near sratio=0 and one will need more sophisticated signal detection schemes.
fitsccd ngc0001.fits - | ccdstat - qac=t
4-dec-2021 document created PJT
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