It was discovered on 2 August 1949, by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory in Heidelberg, Germany.

[1] On 24 April 1989, Ptolemaeus approached the asteroid 6 Hebe within 5.5 million kilometers at a relative velocity of 3.7 km/s.

[2] In the SMASS classification, Ptolemaeus is a common, stony S-type asteroid, which is in agreement with the overall spectral type for members of the Flora family.

[4] Based on a generic magnitude-to-diameter conversion, assuming a Flora-type typical albedo of 0.24, the asteroid measures 5.0 kilometers for an absolute magnitude of 13.7.

He is best known for his influential Almagest, a mathematical and astronomical treatise on the apparent motions of the stars and planetary paths.