Light curves (top) and centroid tracks (bottom) of a compact hot spot orbiting a Schwarzschild black hole for four different orbital radii and inclinations (R/Rg=6 (solid blue), 8 (red dashed), 10 (short-dashed green) and 12 (dash-dotted red)). From left to right the inclinations are 20, 40, 70 and 90°. Since the ordinary centroid for the 90° case simply yields a horizontal line, we instead plot the orbital phase Θ(t) against x(t) (based on the NERO code (Bauböck et al., in prep.); see also Hamaus et al. 2009).