Chang–Refsdal lens

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A Chang–Refsdal lens is a point-mass gravitational lens (e.g. black hole) perturbed by constant external shear.[http://www.citebase.org/abstract?id=oai:arXiv.org:astro-ph/0601457 Citebase - The Chang-Refsdal Lens Revisited] {{webarchive|url=https://web.archive.org/web/20070311013315/http://www.citebase.org/abstract?id=oai%3AarXiv.org%3Aastro-ph%2F0601457 |date=March 11, 2007 }}

The name derives from Kyongae Chang and Sjur Refsdal who in 1979 published a paper in NATURE 282, 561. "Flux Variations of QSO Q0957+561 A,B and image splitting by stars Near the Light Path."

The paper illustrated that stars could affect quasar image brightness.