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Calibration Access and Data Handbook

Procedure

The routine converts a corrected (flatfielded, background, deadtime) count rate into magnitude values of the natural system by applying the zero point correction. The input count rate has already been corrected for instrumental effects (as output from routine CAL_PhotoNatural (see sect. 3.5.14) and for background contributions. The definition of the zero point is retrieved from the extension COLORMAG of the CCF component ColorTrans. The zero-points of the different filters are stored as real number in the keywords ZPTFilterID:

ZPTU	zero point of U-filter
ZPTB	zero point of B-filter
ZPTV	zero point of V-filter
ZPTUW1	zero point of UW1-filter
ZPTUM2	zero point of UM2-filter
ZPTUW2	zero point of UW2-filter
ZPTMAGNI	zero point of magnifier
ZPTWHITE	zero point of white light-filter

The count rates conversion is made with the assumption that the full PSF is sampled. In case of partial PSF sampling the magnitudes have to be corrected by the calling task.

The transformation of the input count rate $s_{nat}$ into the natural system $m_{nat}$ (in units of magnitude) is described by the equation:

$$m_{nat}=zpt0-2.5 \log{s_{nat}}$$ (36)

where $zpt0$ is the zero point of the used filter.

The original routine has been aliased as CAL_omNaturalMagnitude.