Springer Verlag, Astrophysics, 1(51), p. 99-111
DOI: 10.1007/s10511-008-0011-8
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The properties of the relativistic rings which show up in images of a source when a black hole lies between the source and observer are examined. The impact parameters are calculated, along with the distances of closest approach of the rays which form a relativistic ring, their angular sizes, and their "magnification" factors, which are much less than unity. Comment: 13 pages, 3 figures