Friedrich Tietjen
![Friedrich Tietjen.](https://upload.wikimedia.org/wikipedia/commons/d/da/Friedrich_tietjen.jpg)
Friedrich Tietjen (1832 in Westerstede, Oldenburg – 1895 in Berlin) was a German astronomer.
He was director of the ''Astronomisches Rechen-Institut'' (ARI) from 1874 until his death in 1895. The Minor Planet Center credits him with the discovery of one minor planet, the 120-kilometer sized asteroid 86 Semele.
The main-belt asteroid 2158 Tietjen, discovered by Karl Reinmuth at Heidelberg Observatory in 1933, was named in his memory. Provided by Wikipedia
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Published: 1998