  Recently considered a very attracting possibility to detect retro-MACHOs,
i.e. retro-images of the Sun by a Schwarzschild black hole. In this paper we
discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons
and propose a procedure to measure masses and rotation parameters analyzing
these forms of mirages. In some sense that is a manifestation of gravitational
lens effect in the strong gravitational field near black hole horizon and a
generalization of the retro-gravitational lens phenomenon. We analyze the case
of a Kerr black hole rotating at arbitrary speed for some selected positions of
a distant observer with respect to the equatorial plane of a Kerr black hole.
We discuss glories (mirages) formed near rapidly rotating Kerr black hole
horizons and propose a procedure to measure masses and rotation parameters
analyzing these forms of mirages. Some time ago suggested to search shadows at
the Galactic Center. In this paper we present the boundaries for shadows
calculated numerically. We also propose to use future radio interferometer
RADIOASTRON facilities to measure shapes of mirages (glories) and to evaluate
the black hole spin as a function of the position angle of a distant observer.
