Named in honor of Harry A. M. Balster (1946– ) and his younger sister Yvonne. Harry is a very active amateur astronomer in Nijmegen, The Netherlands. His main fields of interest are sunspot research and making the general public enthusiastic for astronomy. By profession he is an electronic engineer. When I. van Houten was measuring her plates at Nijmegen, Harry always helped when there was something wrong with the measuring engine. His sister was a programmer and general assistant in the Nijmegen astronomy department, and she was just as great a help for I. van Houten as her brother. (M 23541; M 25351) _ _.