It looks straightforward. Skipping basically all the maths, it's equation 19 in the paper. Each contour is a line of constant z (flux), plotted in polar coords:

It looks straightforward. Skipping basically all the maths, it's equation 19 in the paper. Each contour is a line of constant z (flux), plotted in polar coords: http://adsabs.harvard.edu/full/1979A%26A....75..228L http://adsabs.harvard.edu/full/1979A%26A....75..228L You plug in the viewing angle, black hole mass and some other constants which are defined in the paper (might need some fiddling to get them to look nice). Then I think the plotter is just some monte carlo sampling and then inverted.