Named in memory of Friedrich Tietjen (1832–1895), professor of astronomy at Berlin University and director of the Astronomisches Rechen-Institut since 1874. For many years, he served as an editor of the respected Berliner Astronomisches Jahrbuch and Nautisches Jahrbuch. After a 13-year period of observations of minor planets and comets, Tietjen became the most prolific orbit computer of the ARI. (M 18447) _ _.