While working at the Bilk Observatory in Düsseldorf, Germany, he searched for asteroids and discovered 24 of them between 1852 and 1890.

[3] Luther married Caroline (nee Marker) and they had one son, William.

[1][2] Two of his discoveries are now known to have unusual properties: 90 Antiope, a binary asteroid with equal components, and the extremely slow-rotating 288 Glauke.

The asteroid 1303 Luthera and the lunar crater Luther were named in his honour.

[5] In 1869, a commemorative medal honoring the discovery of the 100th asteroid shows the profiles of John Russel Hind, Hermann Goldschmidt and Robert Luther.