  The equations of null geodesics in the STU family of rotating black hole
solutions of supergravity theory, which may be considered as deformations of
the vacuum Kerr metric, are completely integrable. We propose that they be used
as a foil to test, for example, with what precision the gravitational field
external to the black hole at the centre of our galaxy is given by the Kerr
metric. By contrast with some metrics proposed in the literature, the STU
metrics satisfy by construction the dominant and strong energy conditions. Our
considerations may be extended to include the effects of a cosmological term.
We show that these metrics permit a straightforward calculation of the
properties of black hole shadows.
