Scheme of the iterative flux and luminosity correction taking the temperature estimate, the K-correction and the missing flux correction into account. In the first part the nominal flux, F_n, is calculated by assuming a temperature of 5 keV and a redshift of zero. In the second part, in the loop comprising steps 4, 5, 6, an improved flux and luminosity is calculated taking the estimated temperature and measured redshift into account. In the third part comprising steps 7, 8, 9 the missing flux is taken into account and once more a better temperature estimate is included in the new flux and luminosity calculation.