  The Marshall Grazing Incidence Spectrometer {\it MaGIXS} is a sounding rocket
experiment that will observe the soft X-ray spectrum of the Sun from 24 - 6.0
\AA\ (0.5 - 2.0 keV) and is scheduled for launch in 2021. Component and
instrument level calibrations for the {\it MaGIXS} instrument are carried out
using the X-ray and Cryogenic Facility (XRCF) at NASA Marshall Space Flight
Center. In this paper, we present the calibration of the incident X-ray flux
from the electron impact source with different targets at the XRCF using a CCD
camera; the photon flux at the CCD was low enough to enable its use as a
"photon counter" i.e. the ability to identify individual photon hits and
calculate their energy. The goal of this paper is two-fold: 1) to confirm that
the flux measured by the XRCF beam normalization detectors is consistent with
the values reported in the literature and therefore reliable for {\it MaGIXS}
calibration and 2) to develop a method of counting photons in CCD images that
best captures their number and energy
