  Recently Holz & Wheeler (2002) 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
Falcke et al. (2000) 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.
