  Combinations of advanced X-ray sources and zero-noise detector of enormous
dynamic range have significantly increased the opportunity of mapping the
reciprocal space of crystal lattices. It is particularly important in the
design of new devices based on epitaxial thin films. In this work, we present a
simple approach to the three-dimensional geometry involved in plotting
reciprocal space maps, along with an example of computer codes to allow X-ray
users to write their own codes. Experimental data used to illustrate an
application of the codes are from antimony telluride epitaxial film on barium
difluoride substrate.
