Named in memory of Heinrich Siedentopf (1906–1963), professor of astronomy and director of the observatories in Jena (1933–1945) and in Tübingen (1949–1963). His research activities covered stellar atmospheres, in particular the theory of convection and solar granulation, interplanetary matter, optics of the earth’s atmosphere, and astronomical instruments. He introduced the iris-diaphragm method for photographic stellar photometry. Together with O. Heckmann and W. Fricke {see planets  (1650) and  (1561), respectively} he was one of the German promoters of the European Southern Observatory. (M 21611) _ _.